1

Question 1

Cell Theory

Answer 1

All organisms are composed of cells

Cells are the basic unit of life

All cells come from preexisting

*viruses are not composed of cells, not an organism

Question 2

Eukaryotic

Answer 2

membrane bound organelles, capable of mitosis

*mature red blood cells don’t have nuclei, expel it during maturation process

Question 3

Prokaryotes vs Eukaryotes

Answer 3

Prokaryotes: 1 circular DNA chromosome

Eukaryotes: many linear chromosomes composed of chromatin, nucleus held by double phospholipid membrane (nuclear envelope) which is porous
- Pores are protein complexes which allow exchange of biomolecules (RNA, protein)

Question 4

Nucleoli

Answer 4

Dense regions in nucleus which assemble ribosomes

Question 5

Cytoplasm

Answer 5

Contains organelles suspended in cytosol, where sub cellular components are trafficked.

Question 6

Endosymbiotic Theory

Answer 6

Mitochondria arose when a bacterium was engulfed by another cell and used for energy

Question 7

Mitochondria

Answer 7

Contain circular mtDNA that make some proteins
Maternally inherited, all mitochondria come from egg

• Cell can contain thousands, mutations in mtDNA lead to serious disorders
• Replicate via binary fission independently of cell like bacteria, DNA replicated and cell splits

Powerhouse of the cell, make cells energy

Question 8

Mitochondrial Matrix: what processes occur?

Answer 8

Makes ATP using citric acid (Krebs) cycle

• Electron transport chain and ATP synthase embedded in inner membrane
• Inner membrane invaginate (folds back on itself to form pouch) as cristae (increases surface area)

Question 9

Endoplasmic Reticulum (ER)

Answer 9

continuous with nuclear envelope
Rough and Smooth ER

calcium storage, protein synthesis and lipid metabolism.

Question 10

Rough ER

Answer 10

Ribosomes embedded which synthesize proteins fed to rough ER for 3D folding and modification

• Glycosylation: add carbohydrate group
• Proteolytic cleavage
• Disulfiide bridges

Membrane bound ribosomes usually form secreted proteins/membrane bound proteins

• Free ribosomes in cytoplasm synthesize intracellular proteins

Question 11

Smooth ER

Answer 11

1. No ribosomes
2. lipid metabolism
3. steroid hormone precursor synthesis (cholesterol)
4. detoxification (liver cells have extensive smooth ER)
5. stores calcium in muscle cells for contraction

synthesizes lipids, phospholipids as in plasma membranes, and steroids. Cells that secrete these products, such as cells of the testes, ovaries, and skin oil glands, have an excess of smooth endoplasmic reticulum.

Question 12

Golgi apparatus (post office)

Answer 12

Once protein is synthesized, packaged into vesicles and sent to Golgi apparatus (post office)

• chambers called cisternae
• receives transport vesicles at cis face, modifies them and send to trans face, then they leave

Question 13

Lysosome

Answer 13

garbage disposal, extracellular stuff enters cell through endocytosis
- vesicle pinches off from cell membrane then fuses with lysosome

Autophagy: intracellular waste fuse with lysosome for degradation

• Digestive enzymes in lysosomes function at acidic pH, pH of cytoplasm is basic so they can’t function

Question 14

Peroxisome

Answer 14

Accumulates and neutralizes peroxides, protect against oxidative stress

• *- Peroxides:** generate reactive oxygen species harmful to the cell
• Peroxisome breaks down fatty acids through beta oxidation
• Formed in ER

Question 15

Cytoskeleton fibers (3 types)

Answer 15

Fibers that act as structure

1. Microfilaments (smallest)
2. Microtubules
3. Intermediate filaments (largest)

Question 16

Microfilaments

Answer 16

Two intertwined strands of actin polymers (F-actin)
- single actin monomer is a globular protein called G-actin

Cell movement and formation of cleavage furrow (indentation of the cell’s surface that begins the progression of cleavage) and interact with protein myosin to initiate muscle contraction

Polar

Question 17

Microtubules

Answer 17

wider, polymers of a-tubulin and B-tubilin

1. Maintain structural integrity of cell
2. Highways for motor proteins to traffic vesicles
3. Form mitotic spindles (separate chromosomes)
4. In Eukaryotic flagellum and cilia, involved in cell motility

Polar

Question 18

Kinesin

Answer 18

Traffics vesicles OUTWARD of cell

Question 19

Dynein

Answer 19

Traffics vesicles INWARD

Question 20

Centrosomes

Answer 20

Composed of two centrioles, microtubule organizing centers

Question 21

Flagellum

Answer 21

Tail of cells such as sperm, moves back and forth powered by ATP in Eukaryotes to move

*In Prokaryotes, use rotary motion and powered by proton gradient, composed of flagellin protein and not microtubules

Question 22

Cilia

Answer 22

Help move substances along cell surface

ex. in lungs cilia help clear out mucus and line Fallopian tubes (egg –> uterus)

Question 23

Polarity of microtubules and microfilaments

Answer 23

Used for polymerization and depolymerization, adding monomers to positive end and removing from negative end
- Treadmilling: both at same time

Question 24

Capping proteins

Answer 24

Halt polymerization, prevents growth and shrinkage

Question 25

Intermediate filaments

Answer 25

Melting pot of protein polymers that provide structural support to cell

• Cell to cell adhesion processes
• *Lamin:** intermediate filament that provides structural support to nucleus
• *Keratin:** hair, skin, nails

Question 26

1 amu =

Answer 26

1 Dalton = 1.66E-27 kg

Mass of one proton/one neutron

Question 27

Electrons

Answer 27

Magnitude of charge is equal to 1.6E-19 Coulombs

Electrons closest to nucleus are lowest in energy, most
stable
- Valence electrons most reactive

Question 28

Atomic weight

Answer 28

avg mass of all isotopes using mass of respective abundancies

Question 29

Molecular weight

Answer 29

weight of a molecules different atoms summed

Question 30

Ions

Answer 30

atoms that lose/gain valence shell electrons
- cations and anions

Question 31

Polyatomic ions

Answer 31

ions composed of more than one atom

Question 32

Nomenclature of anions/cations

ous or ic is more?

ate or ite is more?

Answer 32

Elements with more than one cation indicated by Roman numerals or suffixes -ic and -ous
ex. Fe2+ = Iron (II) = Ferrous ion
Fe3+ = Iron (III) = Ferric ion

Monatomic atoms use suffix -ide
ex. Hydride, oxide

Anions with oxygen = oxyanions

1. hypo___ite (less oxygens)
2. ___-ite
3. ___-ate
4. per___ate (more oxygens)

Carbonate = CO3^2-
Hydrogen carbonate = HCO3^2-

Question 33

The Bohr Model (picture)

Answer 33

Energy levels, quantum numbers
n=1 is the ground state, for an electron to jump to a higher energy level it must absorb energy in the form of a photon of light (“excited”)
- High to low, electron emits a photon of light
- Energy is electromagnetic radiation (visible light, gamma rays)

Question 34

Energy of a photon equation

Answer 34

E = hf

f = c/(λ)

E = hc/λ

h= planck’s constant (6.626 x 10e-34 J/Hz)
f=frequency
(λ)= wavelength

Question 35

Measuring quanta (Rydberg formula)

Answer 35

When electron jumps energy levels, energy is emitted or absorbed in discrete amounts called quanta
- Atomic emission/absorption spectrum is unique to each element

change in E = hc/λ = R(1/ni^2 - 1/nf^2)

R= 2.18 E-18 J
h=plancks
n= energy level initial and final

Question 36

Quantum numbers

Answer 36

shell, subshell, orbital, and momentum within orbital

Question 37

Heisenberg uncertainty principle

Answer 37

exact position and momentum of an electron can’t be simultaneously measured

Question 38

Pauli exclusion principle

Answer 38

no two electrons in an atom can have same 4 quantum numbers

Question 39

Principle quantum number (n)

Answer 39

energy level
- higher # = higher energy

Question 40

Angular momentum quantum # (l)(azimuthal)

Answer 40

subshell, specifies shape of orbital (s,p,d,f)

l=0=s, l=1=p, l=2=d, l=3=f

l = n, (n-1)

If n=1, l=1,0 (both s and p subshells)

Question 41

Magnetic quantum # (Ml)

Answer 41

Specifies spatial orientation of orbital
-l to +l
Each orbital can only hold 2 electrons; s holds 2, p holds 6, d holds 10, f holds 14

Question 42

Spin quantum # (Ms)

Answer 42

negative half or positive half spin (-1/2), (1/2)

Question 43

Electron configuration (picture)

Answer 43

Aufbau principle: fill lower energy levels first
- Electrons always removed from subshell w/ highest electron # (n) first

Question 44

Hunds rule

Answer 44

every orbital in subshell gets 1 electron before any get 2
** half filled and fully filled sub shells are most stable

Question 45

Effective nuclear charge (Zeff)

Answer 45

Attractive force of positively charged nucleus on atoms valence electrons
- if Zeff is stronger, radius is smaller

Question 46

Ionization energy

Answer 46

energy required to remove on valence electron from a neutral atom in the gaseous state
- 1st ionization energy is lower than the 2nd, removal reduces electrostatic repulsion and makes it harder to remove another (hardest to pull from more stable configs)

Question 47

ATP

Answer 47

adenosine triphosphate, source of energy in a cell

• breaking off a phosphate group is energetically favored
• can be coupled w/ energetically unfavorable reactions to drive them forward

Question 48

Two common e- carriers

Answer 48

NAD+ and FAD
- reduced forms are NADH and FADH2

Question 49

Common redox reactions

Answer 49

Glucose and fatty acids are reduced biomolecules that are oxidized in energy producing pathways

A + B –> (A+) + (B-)

Question 50

Polar covalent bond

Answer 50

Electrons distributed on more electronegative side
ex. H-Cl

Question 51

H-bonding

Answer 51

ON/OF

Question 52

Polarity of functional groups (picture)

Answer 52

hydrocarbons -> aldehydes/ketones -> amines -> alcohols -> carboxylic acids -> charged molecules

Polar func groups can be outweighed by larger non polar structures
*Charge outweighs non polar sterics

Question 53

Protein polarity is used for

Answer 53

Enzymes, transmembrane proteins, and folding all use polarity

• active site on an enzyme is specific for its substrate, diff properties disrupt function
• protein folding primarily affected by tertiary structure, interactions b/w side chains of amino acids

Question 54

Plasma membrane permeability

Answer 54

permeable to very small uncharged molecules and lipid soluble non polar molecules

Question 55

Hormones

Answer 55

signaling molecules that travel through the circulatory system to induce various effects on their target tissues

• homeostasis and response to stimuli
• 2 types

Question 56

Peptide hormones (what they’re made of, what they do)

Answer 56

Chains of amino acids, large and polar
- Can’t diffuse into cell, must interact via membrane receptors and secondary messengers (QUICK ONSET< SHORT LASTING)

Question 57

Steroid hormones (what they’re made of, what they do)

Answer 57

derived from cholesterol, non polar
- Can diffuse into cell, interact with nuclear receptors that regulate gene transcription (LONG LASTING)

Question 58

Histone modification

Answer 58

DNA is highly negative, histones act as a scaffolding to package DNA

• Noncovalent interactions (histones positive rich basic amino residues)
• Histones are modified by covalent additions of methyl, phosphate, and acetyl groups
  ex. When acetyl group is added to lysine side group of a histone, removes positive charge which weakens interaction with DNA and creates space for transcription factors –> up regulates gene expression)

Question 59

Metabolic pathways

Answer 59

Glycolysis, Gluconeogenesis, Citric Acid Cycle, beta-Oxidation

Question 60

Glycolysis (what it does and reaction)

Answer 60

Cell to get energy out of glucose without using oxygen
- occurs in the cytoplasm

glucose + 2(NAD+) + 2ADP + 2pi –> 2 pyruvate + 2 ATP + 2NADH + 2H2O + 2H+
*understand what each does and is

Question 61

Committed step of reaction

Answer 61

Steps that are energetically unfavorable tend to be highly regulated

Question 62

Feedback

Answer 62

Early steps tend to be regulated as negative feedback; Final steps can be regulated to monitor end product concentration

Question 63

Basic amino acid structure

Answer 63

Side chain (R), Carboxylic acid (COOH), Amine group (NH2), a-carbon

*side chain gives unique properties

*a-carbon usually a chiral center

-Amines and carboxylic acids act as backbones for polypeptide, side chains stick out to interact with environment

Question 64

Chiral

Answer 64

Non-superimposable mirror images

Question 65

Enantiomers (amino acids)

Answer 65

Can rotate plane polarized light clockwise or CCW
-R or S: based on structure (most aminos are S except for cysteine and glycine which are achiral)

-D or L: based on rotation of PPL (L for naturally occurring amino acids)

Question 66

Non-polar amino acids (largest category)

Answer 66

Side chains either have no polar bonds or predominantly hydrophobic
- Aliphatic (straight chain) hydrocarbon side chains

Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Proline, *Phenylalanine, *tyrosine, *Tryptophan

Question 67

Glycine (Gly, G)

Answer 67

Simplest amino, H side chain, nonpolar
-achiral; doesn’t rotate plane polarized light

Question 68

Alanine (Ala, A)

Answer 68

Methyl side chain (CH3)
- nonpolar

Question 69

Valine (Val, V)

Answer 69

Isopropyl group, nonpolar
- Substitution in place of glutamic acid and hemoglobin causes sickle cell

Question 70

Leucine (Leu, L)

Answer 70

Isobutyl group, nonpolar

Question 71

Isoleucine (Ile, I)

Answer 71

TERTIARY carbon, nonpolar

Question 72

Methionine (Met, M)

Answer 72

nonpolar, 1 of 2 aminos with a SULFUR atom (cysteine)
*C-S bond quite nonpolar
- Found in eggs and DNA methylation

• more inert than cysteine, sulfur is between two carbons

Question 73

Proline (Pro, P)

Answer 73

AMIDE RING, nitrogen is part of side chain

• Gives ability to break up secondary structure of proteins by “proline kinks”
• Almost never find them in a-helices or B-pleated sheets (unless at the turn)

Question 74

3 Aromatic Nonpolar Aminos (Benzene rings)

Answer 74

Phenylalanine, Tyrosine, Tryptophan

• electron delocalization

Question 75

Phenylalanine (Phe, F)

Answer 75

single benzene ring side chain, non polar
- diet soda artificial sweetener

Question 76

Tyrosine (Tyr, Y)

Answer 76

Benzene ring + OH group
- Amphipathic but more nonpolar due to bulky ring

Question 77

Tryptophan (Trp, W)

Answer 77

TWO rings: Amide ring connected to benzene ring
- nonpolar
precursor to serotonin and melotonin

Question 78

Polar but Uncharged Aminos

Answer 78

side chains have 1+ polar bond which shapes its behavior
- Serine, Threonine, Asparagine, Glutamine, Cysteine

Question 79

Serine (Ser, S)

Answer 79

Alcohol side chain, relatively reactive

• polar but uncharged
• targeted by phosphorylation
• post-translational modification and signaling

Question 80

Threonine (The, T)

Answer 80

Secondary hydroxyl group
-polar but uncharged

Question 81

Asparagine (Asn, N)

Answer 81

Amide group (CONH2) 
- polar but uncharged

Question 82

Glutamine (Gln, Q)

Answer 82

methyl then amide group (CH2CONH2)
- polar but uncharged

Question 83

Cysteine (Cys, C)

Answer 83

SULFUR, thiol group (SH)

• sulfur is at end of chain
• not strongly polar but can participate in H-bonding
• 2 cysteine can form covalent disulfide bonds (contributes to proteins tertiary structure/3D shape)

Question 84

Basic Amino Acids (positively charged)

Answer 84

Lysine, Arginine, Histidine

All have +1 charge, NH₃+ side chain and amine group and COO^- carboxyl

Question 85

Lysine (Lys, K)

Answer 85

Protonated amine group, basic amino
- fairly reactive target for methylation, acetylation

Question 86

Arginine (Arg, R)

Answer 86

3 amine groups, most basic amino
- Positive charge can be resonance stabilized

Question 87

Histidine (His, H)

Answer 87

2 amines in one ring, basic
- Under physiological conditions its neutral (deprotonated)

Question 88

Acidic Amino Acids

Answer 88

Functional group readily gives up H+ (negatively charged)

Aspartic acid, glutamic acid

• at physiological conditions, both have charge of -1
  
  • two negative COO^- groups and one NH₃+

Question 89

Aspartic acid (Asp, D)

Answer 89

COOH group

• Aspartate is deprotonated version
• Along with Phe, component of artificial sweetener aspartame

Question 90

Glutamic acid (Glu, E)

Answer 90

Longer hydrocarbon chain before COOH group

• under physiological conditions, deprotonated forms dominant
• Glutamate is deprotonated version
• Important neurotransmitter

Question 91

Atomic Theory

Answer 91

1. All matter consists of indivisible atoms (except radioactive decay)
2. Atoms of same element are identical
3. Compounds = atoms of 2+ elements
4. Chemical reactions are atoms recombining

Question 92

Must know polyatomics

Answer 92

Nitrate, Nitrite, Carbonate, BiCarbonate, Perchlorate, Chlorate, Sulfate, Sulfite, Hydroxide, Chromate, Cyanide, Permanganate, Acetate

Question 93

Intramolecular bonding (between atoms)

Answer 93

Covalent- similar E.N. values, share electrons

• unequal sharing creates polarity
• E.N. differences

Question 94

Types of intermolecular forces

Answer 94

not bonding, between molecules, much weaker than intramolecular forces

1. London dispersion
2. Dipole-dipole
3. H-bonds
4. Ion-dipole
5. Ionic

Question 95

London dispersion

Answer 95

Weakest force can occur b/w any molecules, temporary dipoles arise by chance
*Larger molecules have stronger London forces

Question 96

Dipole-dipole

Answer 96

Polar molecules partial charges

Question 97

H-bonds

Answer 97

Stronger dipole-dipole bonds (more EN atoms)

Question 98

Ion-dipole

Answer 98

Ions and molecules w/ dipole moment

Question 99

Octet rule exceptions

Answer 99

8 electrons in valence shell for both bonding atoms except:

• Hydrogen only req 2 electrons
• Be: 4
• Boron: 6
• 3rd period and below elements can have expanded octet (phosphorus, sulfur)

Question 100

Formal charge equation

Answer 100

= valence e’s - bonds - lone pairs
Molecules try to minimize formal charge

Question 101

Synthesis/combination reactions

Answer 101

2+ reactants –> single product

ex. Haber process
N2 + 3H2 –> 2NH3

Question 102

Decomposition reactions

Answer 102

single compound –> multiple products

• endothermic: energy must be invested to break chemical bonds
  ex. H2CO3 –> H2O + CO2

Question 103

Single displacement

Answer 103

One group replaces another
AB + C –> AC + B
**Often ionic compound, ion replaced by similar
- metal replaces metal, one ion more reactive than the other

Question 104

Double displacement

Answer 104

AB + CD –> AD + BC
**Many pushed forward by producing insoluble precipitate (solid)

Question 105

Neutralization

Answer 105

Acid + base –> H2O + salt
Acid contains H+ and base contains OH, can result in solution with neutral pH depending on concentrations

Question 106

Combustion

Answer 106

Compound reacts (burns) in the presence of oxygen

• hydrocarbon + oxygen –> CO2 and water
• Highly exothermic, release heat/energy
• change in H < 0

Question 107

Oxidation Reduction (redox)

Answer 107

OIL RIG
Characterized by electron transfer
- Oxidized compound gives up electrons, reduced compound gains them

• One of most prevalent reactions in the body
• Oxidation of glucose during cellular respiration, coupling of NADH oxidation and NAD+ reduction, citric acid cycle

Alkanes least oxidized (no bonds with oxygen), alcohols slightly more oxidized with one bond to oxygen, carboxylic acids most oxidized with 3 bonds to oxygen

Question 108

Law of Conservation of Mass

Answer 108

Mass in an isolated system is neither created nor destroyed

Question 109

Peptide bonds are

Answer 109

Bonds that join amino acids to form peptide chains

• N-terminus of one amino to c-terminus of another
• Releases OH of carboxyl group and H (H2O)
• Nucleophilic substitution: lone pair or amine attacks carbonyl carbon

Question 110

Condensation/Dehydration reaction creates?

Answer 110

creates H2O (condensing two molecules into one)

Question 111

What facilitates peptide bond formation and where?

Answer 111

TRNA in ribosomes

Question 112

Peptide bond breaking = (type of rxn)

Answer 112

hydrolysis
- molecule of H2O adds to carbonyl group and kicks off amine group

Question 113

Is peptide bond breaking favorable?

Answer 113

Energetically favorable but extremely slow under physiological conditions (good thing for body)

Question 114

What enzyme catalyzes breakdown of peptide bonds?

Answer 114

Proteases destroy primary structure, also assisted by acidic conditions in stomach (stomach pH is 2 and still requires enzymes to break down proteins)

Question 115

What makes peptide bonds stable under intracellular conditions?

Answer 115

Resonance, gives planar formation that disallows rotation around peptide bond

Question 116

Protein primary structure

When does peptide become dipeptide

Answer 116

linear chain of aminos form backbone of protein, has DIRECTIONALITY

• proteins classified depending on length of chain
• peptide = <50 aminos (dipeptide, tripeptide)

Much harder to disrupt than higher level structures

• product of protein denaturation

Question 117

How is protein size reported? Avg size of one amino?

Answer 117

Reported in molecular mass (kDa); 110 daltons
- 1 dalton = 1 amu = 1 g/mol

Question 118

Protein primary structure directionality

Answer 118

New aminos added to carboxy terminus

Question 119

Protein secondary structure (types)

Answer 119

First layer of protein folding, local regions/small sections
- Alpha helices
- Beta pleated sheets
** backbone interactions, no side chain interactions
- some aminos favor forming a-helices or b-pleated sheets, others known to disrupt secondary motifs
-many proteins have unique secondary structure

Question 120

Alpha helices

Answer 120

Secondary protein structure (backbone interactions)
Common in DNA binding proteins, fits neatly into grooves of DNA helix; stabilized by H-bonds between residues 4 apart (amino to carboxylic group)
- also common in membrane spanning proteins

Question 121

Beta pleated sheets

Answer 121

Secondary protein structure (backbone interactions)
Formed by beta strands, line up next to each other parallel or antiparallel
- implicated role in amyloidosis
- buildup of misfiled proteins, Parkinson’ and Alzheimers
- Proline introduces kinks in chains at turn of sheets

Question 122

Tertiary protein structure

Answer 122

Determines fully folded functional state, 3D shape of polypeptide chain
** Side chain interactions
- Non-covalent, driven by polarity or charge
- Salt bridges (ionic bonds, basic and positive amino and acidic negative side chain bonded)
- Hydrophobic interactions (nonpolar molecules grouping together)
- Disulfide bonds (sulfur atoms of cysteine residues, forms via redox rxn; can be broken by reduction but stronger than ionic and dipole based interactions)

Question 123

Organogenesis

Answer 123

First trimester of pregnancy, major organs develop, fetus continues to grow in 2nd and 3rd trimesters

Question 124

Placenta

Answer 124

Fetus exchanges nutrients, gases, and waste products with mother

• Highly vascularized tissue, brings maternal and fetal circulation into close, but not direct, contact for diffusion of nutrients and oxygen from maternal to fetal blood vessels
• Also diffusion of metabolic waste from fetal to maternal blood vessels

Also secretes hormones

Question 125

Fetal blood vessels

Answer 125

Umbilical arteries (carry deoxygenated blood away from fetal heart) and umbilical vein (carries oxygenated blood to fetal heart)

Question 126

Arteries carry blood ___

Answer 126

Carry blood away

Question 127

Veins carry blood ___

Answer 127

Towards the heart

Question 128

Hemoglobin

Answer 128

Carrier protein responsible for transporting oxygen in the blood

Question 129

Fetal hemoglobin

Answer 129

Especially high affinity for oxygen compared to adult hemoglobin

• can readily steal oxygen from maternal circulation

Question 130

Placenta secretes hormones…

Answer 130

Human chorionic gonadotropin (hCG) (pregnancy tests test for this)

Later progesterone and estrogen to maintain pregnancy

Question 131

Sexual differentiation

Answer 131

Default developmental pathway is female, precursor structure called Mullerian duct develops into uterus, cervix, and upper third of vagina

• Presence of sex determining region (SRY gene) on the Y chromosome halts this progression and reroute toward development of male sexual organs
• Y chromosome: much smaller and contains fewer genes, SRY is “main content”

Question 132

SRY gene

Answer 132

Gene on Y chromosome, codes for transcription factor that causes testes to develop in males; prevents development of uterus and Fallopian tubes

Question 133

Testes

Answer 133

Secrete androgens like testosterone, result in male fetus developing Wolffian duct which later forms male reproductive organs

Question 134

Pregnancy lasts…

Answer 134

37 to 41 weeks, splits into 3 trimesters and culminates into labor and childbirth (parturition)

Question 135

Oxytocin (cuddle hormone)

Answer 135

Exhibits rare example of positive feedback, stimulates uterine contractions during labor

• Contractions induce more oxytocin release from pituitary gland until childbirth

Question 136

What fraction of people diagnosed with cancer in lifetime?

Answer 136

1/3

Question 137

Tumor

Answer 137

Mass of tissue with abnormal cell proliferation, cells divide more than normal cell cyle

• most brain tumors are

Question 138

Benign tumor

Answer 138

Tumor remains localized and contained in one area

• tumor doesnt invade basement membrane and spread to other tissues, a process known as metastasis
• can continue to undergo further mutation and become malignant

Can cause damage to tissue, press on nerves or blood vessels, and a benign brain tumor can be fatal

Question 139

Malignant tumor

Answer 139

Invades through basement membrane and may spread to other tissues and organs

• In order to become malignant and develop into cancer, tumors cells must exhibit uncontrolled growth and gain ability to invade basement membrane and metastasize to other tissues
  
  • form secondary tumors
• Get more aggressive with mutation that allow proliferation and rapid spread
  
  • many cancer cells secrete growth factors and upregulate expression of growth factor receptors
• Also produce proteases that digest components of the extracellular matrix, providing an escape path through basement membrane

Question 140

Cancer

Answer 140

Metastasis of a malignant (virulent or infectious) tumor

• cancer cells frequently secrete factors that promote angiogenesis, the formation of new blood vessels, which provide the highly metabolic tumor with an oxygen and nutrient supply
• In early stages of cancer, tumor antigens may be recognized by immune cells
  
  • destruction of offending cells
  • tumor cells can change how they express proteins on cell surface to avoid recognition
    
    • mRNA, protein, miRNA becomes highly dysregulated compared to tissue of origin

Question 141

Tumorigenesis

Answer 141

Formation of tumors, starts with one cell that is able to bypass normal cell cycle checkpoints and begin to divide abnormally

Can be caused by mutation in a gene that regulates mitosis and cell proliferation

• However, typically begins with an accumulation of mutations in critical genes that together allow a mutinous cell to divide when it shouldn’t, evading normal controls on cell division and growth

Tumor progression driven by process of natural selection, descendant daughter cells proliferate more rapidly, evade the immune system, thrive in anaerobic environment of tumor, and survive other checkpoints will be selected for and predominate in the tumor

Question 142

De novo mutations

Answer 142

In dividing cells, mutations that arise spontaneously due to errors in DNA replication at a rate of about 1 error per 100,000 bp

• Proofreading enzymes catch and repair about 99%
• overall rate of 1 mutation/10 million base pairs
  
  • 6 billion bp in a diploid cell = 600 mutations/1 diploid cell

Question 143

Tissues that divide frequently

Answer 143

Epithelial cells in the skin, liver or digestive tract

• More likely to develop cancer

Most brain tumors are gliomas from supportive glial cells in the brain or metastases from primary tumors located elsewhere

Question 144

Cells that divide infrequently

Answer 144

Neurons

Question 145

Carcinogens

Answer 145

Cancer causing mutagenic agents

• chemicals, radiation (UV, ionizing radiation like X-rays and gamma rays)
  
  • UV radiation known to produce pyrimidine dimers between adjacent bp than if uncorrected can cause lasting DNA damage –> lead to cancer

Cell can survive mutations that occur in noncoding region of DNA or silent mutations in protein encoding genes

• Mutations that occur in critical genes typically trigger DNA repair or apoptosis (cell death) at cell cycle checkpoints, prevent cell from proceeding w/ mitosis
• However, if mutations present in genes that regulate cell cycle checkpoints, cell can escape reulatory mechanisms and continue to proliferate
  
  • will continue to accumulate mutations that allow them to evade other regulatory processes –> positive feedback

Question 146

Chemotherapy

Answer 146

Regimented use of chemical agents (essentially poisions) to treat cancer

• Challenge- specifically targeting cancer cells
• Interfering with cell division (anti-mitotic drugs) affect healthy cells as well with high cell division/cell turnover
  
  • Gastrointestinal symptoms and hair loss

Tumors can also develop chemoresistance, and stop responding to treatments

• more than one drug necessary

Question 147

Oncogenesis

Answer 147

Formation of cancer, characterized by highly dysregulated gene expression favoring synthesis of RNA and proteins that promote growth of the tumor

• Oncogenes and tumor suppressor genes

Question 148

Oncogenes and tumor suppressor genes

Answer 148

1. Oncogenes- mutant genes promoting abnormal cell growth leading to cancer
   
   1. exist as proto-oncogenes that give rise to oncogenes when over-expressed
   2. tend to emerge from genes that code for growth factors, growth factor receptors, transciption factors, protein kinases, and other signaling molecules
   3. also found in cancer causing viurses that either insert oncogenes directly or upregulate existing proto-oncogenes
2. Tumor suppressor genes- genes protecting against abnormal cell growth whose impaired function can lead to cancer
   
   1. block cell cycle progression, respond appropriately to DNA damage, repair DNA damage, prevent changes to cell adhesion
   2. if tumor suppressor is down regulated or mutated, cell is less able to protect against cancer

ex. TP53 gene encodes p53 suppressor protein, “guardian of the genome” (initiates repair or apoptosis), mutation for p53 renders checkpoints useless (50% of human cancers detect this mutation)
ex. BRCA 1 and BRCA 2 genes, repair DNA damage, heritable mutations associated with breast cancer and ovarian cancer (mutations associated with 80% risk in developing breast cancer)
* Genetic screening recommended for those with family history with breast or ovarian cancer

Question 149

Tumor viruses (don’t need to know for MCAT)

Answer 149

Hepatitis B and C viruses (liver cancer)

Papilloma viruses (cervical and anogenital viruses (relating to anus or genitals))

Epstein-Barr virus (causes Burkitt’s lymphoma and Nasopharyngeal carcinoma)

Question 150

Isomers

Answer 150

Molecules sharing the same molecular formula but different structure

Question 151

Stereochemistry

Answer 151

How molecules are arranged in space

• Along with charge interactions, explains why molecules behave the way they do

Question 152

Structural/constiutional isomers

Answer 152

Different ways molecules can be arranged given a molecular formula

functional isomers= structural isomers with different functional groups

Tautomers- structural isomers that exist in equilibrium

• keto-enol tautomers, at room temp keto form is favored
• deprotonated enolate form is also important for some reactions
• also enamine and imines, replace oxygen with nitrogen

** resonance does not equal tautomers

• resonance represents single underlying structure while tautomers require breaking and reformation of bonds

Question 153

Stereoisomers: conformational isomers

Answer 153

Single pattern of connectivity, different spatial configurations

• rotating around single bonds
• rotating around double bonds - cis and trans
• chiral centers with 4 different substituents

Question 154

Visualizing steroisomers

Answer 154

Newman projections - carbon carbon bond extends into page

• eclipsed (unfavorable, torsional strain) formations (0 degrees of separation between bulky substituents)
• staggered (maximize separation between bulky substituents)
• anti conformation = 180 degrees of separation, most favorable
• Gauche effect = less favorable, 60 degrees of separation

Question 155

Angle strain

Answer 155

Angle between single bonded carbon atoms deviates from 109.5 degrees

Question 156

Torsional strain

Answer 156

Eclipsing substituents on neighboring atoms

Question 157

Steric strain

Answer 157

Substituents (even hydrogen) getting in each others way

• to resolve, cyclohexane switches between chair (most stable, prefers), twist boat, and half boat
  
  • substituents can either be axial or equatorial, each carbon has one axial one equatorial (one down and one up)
  • bulkier substituent strain minimized by equatorial
  • cis: two bulky substituents point in same direction
  • trans: bulky substituents point in opposite directions
    
    • both are stable

Question 158

Geometric isomerism

Answer 158

Different orientation of substituents around double bonds

• cis/trans and E/Z classification
• double bonds have fixed planar shape

Cis- identical substituents on same side of double bond

Trans- identical substituents on different sides of double bond

E/Z- doesnt require substituents to be identical

• Z isomers- two higher priority sustituents on same side (zame side)
• E isomers- two higher priority substituents on different side

Question 159

Cahn-Ingold-Prelog Rules (priority rules)

Answer 159

Priority determined by atomic weight of the atoms, heavier = higher priority

• if same, look at amu of atoms attached
• multiple bonds higher priority than single bonds

Question 160

Chirality

Answer 160

Describes asymmetry of molecules in 3D space

Chiral centers- atoms with 4 bonds to 4 distinct groups

• type of sterocenter: atom bonded to 3 unique groups

Chiral if mirror image is distinct and nonsuperimposable

• enantiomers- same chemical formula, share physical and chemical properties
  
  • receptors discriminate for enantiomers

Achiral- molecule has superimposable mirror image (align perfectly)

Question 161

Absolute configuration around chiral center (nomenclature)

Answer 161

Uses atomic mass priority

1. lowest priority substiuent is in back pointing away

• if not, rotate molecule around axis
• Arrow from 1 to 2 to 3
• R= clockwise
• S= counterclockwise

Question 162

d/l Nomenclature

Answer 162

How molecule rotates plane polarized light

• enantiomers rotate PPL in opposite directions
• clockwise = d
• CCW = l

Experimentally determined, limited use

Racemic mixture = 0 degrees rotation

Question 163

D/L nomenclature

Answer 163

Classify aminos and monosaccharides

• Orientation of hydroxyl or amine group at highest number chiral carbon (bottom of Fischer projection)

D- hydroxyl/amine on right side

L- hydroxyl/amine on left side

**Maximum efficiency when carbohydrates/aminos are in same configuration

**assume all carbohydrates are D isomers and aminos are L isomers

Question 164

Enantiomeric excess

Answer 164

ee = observed opitcal rotation/specific optical rotation x 100

Question 165

Number of possible stereoisomers of a chiral molecule

Answer 165

2ⁿ where n = number of chiral centers

If two steroisomers share opposite configuration at each chiral center, they’re enantiomers (nonsuperimposable mirror images)

Question 166

Diastereomers

Answer 166

Molecules with multiple chiral centers that differ at some but not all

epimers- stereoisomers differing at just one chiral center (can also be diastereomers but not always)

Question 167

Meso compounds

Answer 167

Contain internal plane of symmetry (achiral even with chiral centers)

Question 168

Anomers

Answer 168

Cyclic sugar compounds with hydroxyl groups that differ in orientation at chiral carbon/carbon 1 (anomeric carbon)

Glucose has a-glucose and B-glucose

mutarotation- interconversion between a and b forms

Question 169

Ketogenic diet

Answer 169

Eat low carbs and high fats, body enters “ketosis”, fat burning machine (rapid weight loss)

Question 170

Carbohydrates

Answer 170

Essential macronutrient essential to generate cellular energy

• contain C, H, O, name derived from empirical formula C_m(H₂O)n
• made up of monosaccharides (sugars) to form disaccharides, oligosaccharides + polysaccharides
• monosaccharides can take linear or cyclic form

Question 171

Linear monosaccharides

Answer 171

Contain carbonyl (C=O) and at least one hydroxyl group attached to carbon backbone

• if carbonyl is an aldehyde group, making sugar an aldose
• if carbonyl is in middle of backbone, its aketone group and sugar is a ketose

Classified according to number of carbons in backbone

• triose, tetrose, pentose, hexoses, heptoses

Question 172

Fischer projections

Answer 172

3D molecules represented in 2D

Horizontal lines are coming out of page, carbons numbered from top to bottom

Question 173

Cyclic carbohydrates

Answer 173

Most 5 to 6 carbon sugars exist cyclically

• different anomers with different properties
• cyclize via nucleophilic addition where hydroxyl group on 4th or 5th carbon acts as nucleophile and attacks carbonyl carbon

Hexoses can form six membered or 5 membered rings (angle strain too high for any smaller ring)

• sugars in 5 membered rings are furanoses, 6 membered are pyranoses (glucose)
• allows easier nomenclature than IUPAC

Question 174

Hemiacetal

Answer 174

Formed when aldehydes when alcohol attack carbonyl carbon

Hemiketal- the same except second R group instead of aldehyde H

Question 175

Emotion

Answer 175

3 components: cognitive (what comes to mind when feeling emotion), physiological (emotions manifest physically), behavioral (way we behave when feeling emotion; variable)

Have been adaptive in evolutionary trajectory

• question is degree to cultural specificity

Universal emotions: same meaning no matter where someone grows up, hardwired to predictable facial expressions

• happiness: smiling, wrinkling brow
• sadness: corners of mouth lowered, inner side of brows raised
• surprise: opening ones eyes wide and mouth slightly, raising brows
• fear: also involves widening eyes/raising eyebrows, but w/ lips retracted toward ears
• anger: lowering eyebrows, pressing lips together, glaring
• disgust: wrinkling ones nose, lifting upper lip
• contempt: pulling corner of mouth upward

Question 176

Limbic system

Answer 176

Where emotion is rooted in the brain

• grouping of structures in midbrain (vicinity of thalamus in medial part of temporal lobe)
  
  • amygdala: processing emotional stimuli
    
    • has neurons that project to hypothalamus, an important link between nervous and endocrine system; both play important role in translating between stimuli, concious perceptions, and physiological manifestation of emotion
• emotion, motivation, memory

Question 177

Emotions Physiological Effect

Answer 177

Anxiety and fear associated with activation of sympathetic nervous system (autonomic, fight or flight mechanism)

• dilation of pupils, reduced parastalsis, increased conductivity of skin, less blood flow of muscles responsible for digestion, incr blood sugar

Blushing - embarrassment, sweating - nervousness

Question 178

Theories of Emotion: James-Lange Theory (1800s)

developed w/o benefit of modern findings in neurology

Answer 178

Stimulus -> physiological arousal -> emotion

Physiology shapes pyschological perceptions

Incomplete theory of emotion; different people can have different emotional/physiological responses to stimuli

Question 179

Theories of Emotion: Cannon-Bard (1920s)

developed w/o benefit of modern findings in neurology

Answer 179

Stimuli -> physiological response -> cognitive response (depending on context) -> emotion

J comes before S

Experiment- researchers injected subjects w/ either epinephrine (adrenaline) or placebo and told them they were getting a made up vitamin and told they would have different effects (some told they’d have sympathetic effects and others foot numbness, others told nothing)

• while waiting, stayed with researcher who acted euphoric or angry towards them
• subjects handled emotions appropriate to what they were told

Question 180

Theories of Emotion: Schachter-Singer (1960s)

Answer 180

Stimulus -> emotional response and physiological response simultaneously and separately -> jointly lead to behavioral response

Question 181

Theories of Emotion: Lazarus (1970s-90s)

Answer 181

Priveleges cognitive assessment of entire situation

stimuli -> cognitive appraisal -> physiological arousal and emotion

Question 182

Stressors

Answer 182

• Cataclysimic events: external and broad scale
• Events in daily life, transitions

independent stressors: outside of our control

dependent stressors: impacted by our own behaviors, within our control

avoidance conflicts: avoid

approach conflicts: want to approach

• avoidance-avoidance conflict is two bad options
• double approach avoidance- each choice has pros and cons

Question 183

Stress appraisal

Answer 183

Primary appraisal: process through which a person sees an event as a threat or stressor

Secondary appraisal: assessment of ability to deal with stressor

Question 184

Distress

Eustress

Neustress

Answer 184

Distress: form of stress with a negative effect

Eustress: positive stress, brings out the best (ex. athlete playing in big game)

Neustress: neutral stress, no impact

Question 185

General Adaptation Syndrome

Answer 185

How body responds to stress

1. Alarm- sympathetic nervous system activated
2. Resistance- mediated by cortisol, chronic stress response
3. Exhaustion- body’s resource drained, increased susceptibility to fatigue and illness (cortisol drained)

Most well known negative impact of chronic stress is elevated blood sugar levels, increased risk of cardiovascular disease, impairment of immune system

• reduced fertility and greater risk for psychological conditions (like depression)

Big topic of study for socio-economic outcome

Question 186

Learned helplessness

Answer 186

Repeated exposure to stressors that one is unable to change/avoid (eventually stop trying)

• potential links to psychiatric conditions like depression

Question 187

Coping Strategies to Stress

Answer 187

Maladaptive: unhealthy strategies ex. substance abuse, verbal emotional and physical aggression, self harm

• conditions can shape peoples habits

Adaptive: healthy responses to stress ex. meditation and exercise

• context matters: exercise could be associated with eating disorders

Question 188

Motivation

Answer 188

Underlying purpose for our actions

• Biological motivators- hunger, thirst, sex drive
  
  • addiction, obesity, compulsive behaviors
• Sociocultural motivators- varies between cultures

Question 189

Intrinsic and Extrinsic motivation

Answer 189

Intrinsic: comes from inside yourself

• find a certain activity to be rewarding on our own terms no apparent reward
• self sustaining and resilient

Extrinsic: external factors drive behavior

• some other reward (money, prestige)
• vanishes when reward does

Question 190

Instincts

Answer 190

Hard-wired, fixed behavioral patterns

In humans, a behavior not an urge that happens automatically regardless of cultural context ex. urination, defacation and not hunger or thirst

Question 191

Homeostasis

Answer 191

How our bodies maintain themselves to maintain a stable internal environment

• Use of hormones to maintain physiological parameters like blood glucose levels, fluid and electrolyte concentrations

Question 192

Drive

Answer 192

Urge to return some parameter to homeostasis

• Powerful motivators like hunger and thirst, sleepiness

Drive Theory: an excitatory state produced by a homeostatic disturbance

Drive reduction theory: motivation comes from a desire to return to homeostasis

Primary drives: basic, biologically grounded needs

• hunger, thirst, avoiding extreme heat or cold

Secondary drives: less basic needs

• recognition, social prestige, money (grey area)

Question 193

Maslow’s Heirarchy of Needs (motivation)

Answer 193

Can’t focus on higher up needs until basic needs are satisfied

Question 194

Psychological Arousal (motivation)

Answer 194

People are motivated to engage in actions that optimize psychological arousal

• don’t like to be bored or overwhelmed

Yerkes-Dodson Law: performance at various tasks is optimized by medium levels of arousal

Question 195

Incentive Theory of Motivation

Reinforcers (motivation)

Expectancy-value Theory

Self-determination Theory

Opponent process Theory

Answer 195

• Incentive theory of motivation: humans respond rationally to external incentives

Primary reinforcers: rewards that correspond to basic physiological needs

Secondary reinforcers: psychologically complex concepts (recognition or appreciation)

• Expectancy-value theory: motivation is a reflection of the balance between expectancies(how successful we think we’ll be) and values(is task worthwhile)
• Self determination theory: emphasis placed on intrinsic motivation
  
  • people feel inherently motivated to engage in tasks that they are competent at performing
• Opponent process theory: If a certain experience initially provokes an intense reaction, the opposite reaction tends to predominate
  
  • ex. addiction

Question 196

Attitude

Answer 196

Pyschological orientations that people have towards another person, activity, topic

• broad category, if we can direct our attention to something we can have an attitude about it

3 Components:

1. Affective- feelings we have towards something or someone (emotional)
2. Behavioral- how we act (shaped by affective and cognitive)
3. Cognitive- underlying analytical perceptions

Question 197

Effects of behavior on attitude:

Foot in the door technique

Answer 197

Induce compliance to a large technique by first getting someone to agree to a small request

Question 198

Effects of behavior on attitude:

Role-playing

Answer 198

Simulating behavior can shape one’s attitudes

Question 199

Effects of attitude on behavior:

Thomas theorem

Answer 199

If people define situtations as real, those situations have real consequences

Question 200

Effects of attitude on behavior:

Cognitive dissonance theory

Answer 200

The discrepancy when a certain attitude or behavior is confronted with conflicting evidence

• People modify behaviors to match attitudes or vice versa
• ex. addictive/compulsive behaviors, anti-vaccine movement

Ways of relieving cognitive dissonance:

• acknowledge conflicting evidence, appeal to justifications, acknowledge risk but create hypothetical considerations or plans, downplay the risk, cast doubt or express skepticism

Question 201

Elaboration-Likelihood Model (different ways of being persuaded)

Answer 201

Central route of processing: rational decisions based on advantages and disadvantages of choices

• Deeper thinking/processing, more stable outcomes

Peripheral route: superficial decisions based on gut reactions and surface level characteristics

• Less stable

Question 202

Social Cognitive Theory (attitude and behavior)

Answer 202

Modeling desired attitudes and behaviors can be a strong method of changing attitudes

• establishment of social norms can also be very persuasive

Question 203

Influencing Human Behavior

Answer 203

• Appeal to central or peripheral route processing
• Targeting message to appropriate group
• Appealing to social factors
• Persuasion can be resisted by using central route reasoning or encountering cognitive dissonance
  
  • patterns of denial and minimization that result from cognitive dissonance

Question 204

Classical Conditioning (paradigm)

Answer 204

Pavlov’s Dogs- dogs salivate in respone to smell of meat

• paired the smell of meat with a metronome, salivated in response to the metronome
• Smell of meat = unconditioned stimulus
• Salivating = unconditioned response
• Metronome at beginning = neutral stimulus

Acquisition= successful conditioning

After acquisitioning smell of meat to the metronome, salivating becomes conditioned response and metronome becomes conditioned stimulus

Extinction= eventually, without pairing, the conditioned response will go away (habituation, repeated stimuli elicit a diminished response over time)

• spontaneous recovery= conditioned response re-emerges without another conditioning process
• stimulus generalization= stimuli similar to the conditioned stimuli may evoke the conditioned response
  
  • discrimination= ability to distinguish similar stimuli

Dishabituation= intervening stimulus resensitizes person to original stimulus

Question 205

Types of Historically Important Experiments:

Answer 205

1. Those that discover a new fact or phenomenon
2. Those that shed light onto previously unknown mechanisms underlying familiar behavior
   
   1. Pavlov’s dog experiment

Question 206

Operant Conditioning (B.F. Skinner)

Answer 206

Reward (reinforcers)

reinforcment: anything that increases the frequency of a behavior

• positive stimulus (something is added) or negative stimulus (something is removed)
• positive or negative reinforcement

punishment: anything that decreases the frequency of a behavior

• positive stimulus(something added to punish) or negative stimulus (something taken away to punish)
• positive or negative punishment

Escape learning: learning a behavior to terminate an aversive stimulus (ex. turning off an alarm clock)

Avoidance learning: learning a behavior to prevent an aversive stimulus from occuring

Continuous reinforncement: provide reinforcement everytime behavior is performed; extremely effective but hard with limited resources

Partial reinforcement: reinforcement applied in some cases

• variable more effective than fixed
• ratios more effective than intervals
• variable ratio schedule is fastest for acquisition (casinos with slot machine)

Shaping: gradual approximation of a target behavior

Instinction is a concern similar to classical conditioning; instinctive drift

Question 207

Behaviorism

Answer 207

B.F. Skinner, psychology studied through observable behavior rather than guessing internal states

Question 208

Operant conditioning with classical conditioning

Answer 208

Use primary reinforcer (stimuli an animal is biologically programmed to respond to) and use classical conditioning to associate it with a neutral stimuli = conditioned/secondary stimulus

Question 209

Latent learning

Answer 209

subconscious retention of information without reinforcement or motivation

Question 210

Observational Learning

Answer 210

Learning can happen merely through observation

• Alfred Bandura (1961) children watch adults hit bobo dolls (bounce back up when hit) and hit them themselves

imitation is a subtype but people extrapolite observations to their own context

Can be a source of learning of what not to do

Mirror neurons- fire when someone is performing an action and also observing a similar action, contribute to observational learning

• also contribute to empathy, feeling someones emotions from their perspective

Question 211

How memory is processed in our mind (2)

Answer 211

Encoding- store and perform cognitive processes on

Can process environmental input automatically or deliberately

• Conscious and unconscious techniques affect the ease of encoding
• Priming: effect of context on our ability to perceive stimuli
  
  • positive and negative
• Chunking: complex stimulus broken down into smaller easier to encode components
  
  • Mnemonics
• Method of loci: mentally mapping info onto an imaged space (like a house w different rooms)

Pyschological arousal restricts our focus of attention

Question 212

Sensory memory

Answer 212

Sensory memory- instantaneous, at any given time, temporarily stored and will decay in matter of seconds without rehearsal/reinforcement

Question 213

Long-term memory

Answer 213

Long-term memory- hours to years, storage not limited

• semantic (explicit) memory- memory of specific pieces of information (ex. trivia)
• procedural (implicit) memory- memory of how to do something (ex. riding a bike)
• episodic memory- memory of experiences
  
  • misinformation effect (memory retrieval): information we subsequently obtain can affect how we remember the original event
    
    • can cause witnesses in a trial to be biases; once they learn someone is a criminal they see them in a certain light during past memories

Question 214

Short term/working memory

Answer 214

Short term- tens of seconds to minutes, limited capacity

Working memory- cognitive and attentional processes used for short term memory

visuospatial sketchpad: a buffer that holds on to visual and spatial memory as it’s processed by working memory

Question 215

Flashbulb memory

Answer 215

Many of us have experienced having extrememly vivid memory of moment in our lives (usually emotion)

Question 216

Eidetic (photographic) memory

Answer 216

Ability to remember a stimulus in great detail after a relatively short exposure

Question 217

Iconic memory

Answer 217

How a highly detailed visual image can remain in our perceptin after the stimulus itself is removed

Question 218

Prospective memory

Answer 218

Memory about plans to do something in the future

Question 219

Memory storage

spreading activation-

schemas-

source monitoring errors-

Answer 219

Stored in semantic networks- heirarchical storage, linear top down approach; doesnt capture everything

• also have to account for metaphorical or emotional associations
• ex. rocking chair stored chair category in furniture category
• spreading activation- when a concept is brought to mind, spreads to adjacent nodes of network
  
  • schemas- ways in whcih we organize our knowledge about the world
  • source monitoring errors- memory or knowledge is correct but misattribute its source

Question 220

Memory retrieval

Answer 220

Process of calling upon memories and stored knowledge

• distinction between recall (active) vs. recognition (passive)(easier than recall, req shallower knowledge)
• semantic activation- can more quickly retrieve adjacent concepts

Several factors can help or hinder recall of items:

• Serial position effect: extreme ends easier to recall
  
  • Primacy effect- people more likely to recall items at the beginning of a list than in the middle
  • Recency effect- items at the end of a list are easier to recall than the middle
• Spacing effect: recall more effective when learning process is spaced out
• Dual coding effect: studying multiple modalities is more effect than one

Question 221

Emotion and memory retrieval

Answer 221

Emotions can also effect memory retrieval, emotionally intense memories more likely to be stored

Being in a certain mood might favor recollection of similar emotional overtone

State-dependent effect- certain mood might promote the recall of memories that were encoded when you were in a similar mood

• also applies to states of consciousness (drugs)
• being in the same physical setting where a memory was encoded and stored can promote its recall

Reproductive memory: we encode info and reproduce it as needed; insufficient oversimplification

• In reality, memory is reconstructive: we build memories based on our perceptions of ourselves and others, context of events, etc.

False memories: (often not deliberate) memories reconstructed and not recorded

Question 222

Memory loss

Answer 222

Inevitable; relearning is faster than learning the first time, each successive round more successful

• Ebbinghaus forgetting curve: repeated rounds of learning slows down the forgetting process and consolidates more information into long-term memory

Interference

• Proactive interference: old memories inhibit the consolidation/retrieval of new ones
• Retroactive interference: new memories/knowledge interfere with older memories

Amnesia: losing memories of entire experiences, periods of time and/or information

• retrograde: inability to remember previous events
• anterograde: the inability to form new memories
• Alzheimer’s disease: majority of long term dementia cases
  
  • characteristics: neurofibrillary tangles involving tau proteins and plaques composed of beta-amyloid proteins
  • forgetfulness and short term memory loss, progresses to more severe anterograde and retrograde , cognitive deficits, difficulties thinking, speaking, and emotional disturbances
  • no known cure, no established preventive measures
• Korsakoff’s syndrome: causes anterograde and retrograde amnesia
  
  • confabulation: creating elaborate fictional stories
  • caused by a deficiency of thiamine (Vitamin B1)
  • severe alcoholics and eating disorders
  • preventable through proper nutrition

Aging does reduce fluid intelligence and speed of acquiring knowledge, but does not cause loss of previously acquired knowledge and crystallized intelligence

Question 223

Biology of memory

Answer 223

Synaptic connections:

• formation
• strengthening
• pruning or loss
  
  • important stage of early childhood development
    
    • autism

Nueroplasticity- ability of brain to rewire itself in response to learning new information or to compensate for disease or injury

• contributes to lifelong learning

Long term potentiation- strengthening, formation of synaptic connections

Question 224

Solids

Answer 224

Fixed shape and volume, particles don’t flow or move past each other

• amorphous- no order to particles, not quite as rigid
  
  • glass, gels, polymers like rubbers and plastics
• crystalline- highly ordered, repeating pattern
  
  • table salt
  • 4 types
    
    • Ionic- made up of ionic compounds
    • Molecular- molecules held together by non-ionic molecular forces
      
      • ice
    • Covalent network- covalent bonds
      
      • diamonds with carbon atoms
    • Metallic solids- metallic atoms with metallic bonds
      
      • delocalized valence electrons give conductive properties

Question 225

Liquids

Answer 225

No fixed shape, hard to compress, flow readily

Viscosity- resistance of liquid to flow

Surface tension- amount of energy needed to increase surface area of a liquid

• tension created at liquid surface by intermolecular attractions
  
  • stronger than intermolecular attractions with surroundings
• Cohesive forces- attractive forces between same type of molecules
• Adhesive forces- attractive forces between different types of molecules
  
  • capillary action- movement of a liquid up sides of tube against gravity

Question 226

Gases

Answer 226

Flow and have no fixed shape but readily compressible/expandable

• Particles free moving and spaced apart, little intermolecular interactions
  
  • move randomly
• Pressure- amount of force particles exert on surroundings

Question 227

1. Solid transitions to liquid
2. Liquid becomes gas
3. Gas becomes liquid
4. Liquid to solid
5. Solid becomes gas
6. Gas becomes solid

Answer 227

1. Melting/fusion
2. Vaporization
3. Condensation
4. Freezing
5. Sublimation
6. Deposition

Question 228

Gibbs free energy (G)

Answer 228

∆G > 0 = nonspontaneous

∆G < 0 = spontaneous

• ∆G= ∆H - T(∆S)
  
  • • H = enthalpy; energy (like heat)
      
      • increases is thermodynamically unfavorable, ∆G more positive
  • S = entropy; randomness, highest in gases
    
    • energetically favorable, contributes to more negative ∆G (more spontaneous)

Question 229

Enthalpy (∆H)

Answer 229

H = E + PV

E= internal energy

Question 230

Q = mc∆T

Answer 230

How much temperature changes from addition of heat

Q= heat added (kJ)

m = mass (kg)

c = specific heat capacity (kJ/kg x K)

∆T = temp in Kelvin

Specific heat capacity of water is higher than of ice, liquid water can absorb more heat

Question 231

Heating curve

Answer 231

For heating curves, temp increases until reaches value the bonds become broken and thats where phase change occurs

∆H_f = enthalpy of fusion = how much heat is needed to melt one mole of substance (kJ/mol) = Q/m (kJ/kg)

334 kJ/kg for water (energy required to melt 1 kg of ice)

∆H_vap= enthalpy of vaporizationm= Q/m

If we’re melting a block of ice into gas, have to conside q=mc∆T + ∆H_vap + ∆H_f

Question 232

Phase Diagram

Answer 232

• Pressure (atm) on y axis
• Temp (K) on x axis

Phases in equilibrium along boundary lines

triple point- all three phases in equilibrium

critical point- beyond which, liquid and gas phases become indistinguishable

• beyond critical point, liquid/gas is super critical fluid

Question 233

Alcohols (naming)

Answer 233

Organic compounds that contain hydroxyl (OH) group

• suffix -ol (ex. 2-pentanol, if OH is on carbon 1 its number is ommited, like ethanol)
• diol has two carbon substituents
• common naming adds -yl, ex. propyl alcohol
• when OH isn’t highest priority, hydroxy- prefix

Question 234

Alcohol properties

Answer 234

Melting and boiling points are high due to H-bonding, increases with additional OH’s

• Alcohols are weakly acidic (pKa from 15-17, weaker than water)
  
  • can be made stronger by adding electron accepting substituents (like adding a chlorine) and weaker with electron donating
  • ***anything that pulls electrons from oxygen in OH group makes acid stronger, easier for H to leave
  • Adding alkyl groups makes alcohol more basic
• *** all acids and bases have this ability but alcohols have wide range of pKa values

Question 235

Conjugate base of an alcohol (deprotonated)

Answer 235

Alkoxide- strong base (***weaker the acid = stronger the base)

Question 236

Alcohol as functional group (reactions)

Answer 236

Can react with oxidant to form ketone or aldehyde, acid/base reaction to form ether; can also form alkenes, thiols. epoxides and halohydrins

• Makes alcohols essential for pharmaceuticals, organic industrial materials

MCAT televant reactions:

• Oxidation-**increase in number of bonds to electronegative element or decrease in bonds to H
  
  • energy released by spontaneous redox reaction is converted to electrical energy
  • Reduction is the opposite, increase in bonds to H, but alcohols undergo oxidation

Question 237

Alcohol oxidation

Answer 237

Weak oxidizing agent (common one is PCC) converts alcohol to carbonyl

Stronger oxidizing agent converts alcohol to carboxylic acid (sodium dichromate, potassium dichromate, chromium trioxide)

• Only one step away from carbon dioxide (most oxidized form of carbon)
• secondary alcohols can only become ketons, tertiary can’t be oxidized

Metal + oxygen atoms = oxidizing agent

Question 238

Alcohol protection in reactions

Answer 238

Want to react something other than alcohol in a reaction, must protect it (make it unreactive) with a protecting group: Silyl ethers, mesylates, tosylates

• silyl ethers: use silyl chloride and alcohol; to get alcohol back, treat substrate with fluoride ion to break Si-O bond
• mesylate: react alcohol with methanesulfonyl chloride
• also make alcohol into better leaving group without adding acid
• tosylate: react alcohol with toluenesulfonyl chloride
• also make alcohol into better leaving group without adding acid

Alcohols can also be used to protect other functional groups (carbonyls)

Question 239

Phenols

Answer 239

Hydroxyl group added to aromatic benzene ring

• more complex phenols can be created with additional substituents

Especially acidic due to aromaticity (acid strength = stability of conj base)

• without H on OH group, resonance throughout ring
• if add electron withdrawing substituents, can lower pKa enough to act as acid

Nomenclature

• ortho(adjacent), meta (one carbon separation), and para (two carbon separation) describe orientation of two substituents on ring relative to each other

Question 240

Phenol oxidation/Quinone

Answer 240

Hydroquinone (p-benzenediol) can be oxidized to form Quinone (becomes nonaromatic)

Quinones- electron acceptors that participate in biochemical reactions

• Ubiquinone (Coenzyme Q): liquid soluble electron carrier that hangs out in inner mitochondrial membrane to facilitate electron flow through complexes I, II, and III of ETC
• Can carry one or two electrons
  
  • when carrying one, one carbonyl group reduced to an alcohol (Ubisemiquinone)
  • when carrying two, both carbonyls reduced and called ubiquinol

Question 241

Conjugation

Answer 241

have alternating single and multiple (here, double) bonds. This alternation allows for the overlap of p orbitals and the delocalization of electron density.

Question 242

Protic

Answer 242

solvent that has a hydrogen atom bound to an oxygen (as in a hydroxyl group), a nitrogen (as in an amine group), or fluoride (as in hydrogen fluoride). … The molecules of such solvents readily donate protons (H+) to solutes, often via hydrogen bonding.

Water is the most common protic solvent

Question 243

Pyruvate

Answer 243

Pyruvate: simplest alpha-keto acid (part ketone, part carboxylic acid)

• “2-oxopropanoic acid”

Question 244

Carbonyl a-hydrogen (ketones and aldehydes)

Answer 244

The hydrogens on an alpha carbon, which are known as alpha-hydrogens, are weakly acidic and can be removed by a strong base.

• negative charge left behind when H is removed is stabilized by resonance (stabilized conj base raises acidity)
  
  • negative charge shifted to Oxygen (happier on more electronegative atom)
    
    • ***= ENOLATE; deprotonated form of enol
  • Not the same thing as keto-enol tautomerism, which doesn’t involve deprotonation

When the negative charge from deprotonation is on the alpha carbon and not oxygen, just as important for reactions

alpha carbon- any carbon adjacent to carbonyl carbon

Question 245

Enol and Enolate

Answer 245

enol- combines alkene group (“en”) and hydroxyl group (“ol”)

Question 246

When talking about aldehydes and ketones, also talking about biologically relevant molecules like

Answer 246

Pyruvate (major product of glycolysis), pyruvic acid

Question 247

Ketones

Answer 247

Carbonyl bonded to two carbons

IUPAC suffix “-one”, carbonyl assigned lowest possible number if highest priority

• prefix “keto-“ or “oxo-“ for carbonyl
• common names-
  
  • “acetone” simplest ketone, two methyls; common household paint thinner/nail varnish remover

Ketones can form hydrogen bonds, but they can only act as the acceptor (accepting the hydrogen) and not the donor. Ketones accept a hydrogen bond via the carbonyl oxygen

Question 248

Aldehydes

Answer 248

Carbonyl bonded to a carbon and a hydrogen

IUPAC suffix “-al” and prefix

• if attached to a ring, may use suffix carbaldehyde
  
  • ex. cyclopentanecarbaldehyde

Question 249

Aldehyde and Ketone physical and chemical properties

Answer 249

Carbonyl double bond is highly polar = polar aprotic; capable of dipole-dipole interactions with other molecules but not hydrogen bond donors

• makes aldehydes and ketones ideal solvents for organic reactions; specifically S_N2 reactions
  
  • can dissolve polar reagents but not strong enough nucelophiles to interfere with reaction

Higher melting and boiling points than alkanes of similar size due to polarity; not as high as alcohols or carboxylic acids

*ketones less acidic than aldehydes due to extra electron donating group, tougher to lose alpha hydrogen

beta-dicarbonyl compounds- two carbonyls connected to alpha carbon, tend to be considerably more acidic due to both pulling electrons from a-carbon

Question 250

Aldehyde and ketone reactions

Answer 250

Oxidation of glucose during cellular respiration, coupling of NADH oxidation and NAD+ reduction, citric acid cycle; At the heart of these reactions:

• glucose = aldehyde
• oxaloacetate and pyruvate = ketoacids

Aldehydes and ketones can function as both nucleophiles and electrophiles

• two reaction sites: carbonyl carbon = electrophile (partial positive) and alpha carbon = nucleophile (negative once hydrogen is removed)
• depending on if neutral or deprotonated, can tell how they’ll function in reaction
  
  • also lookout for other components of reaction environment, like a strong base that could convert aldehyde/ketone

Aldehydes carbonyl carbon more reactive than ketones due to steric hindrance, carbonyl carbon in ketones harder to access

Question 251

Oxidation of aldehydes/ketones

Answer 251

Oxidation of aldehydes to carboxylic acids:

• requires strong oxidizing agent (KMnO₄)(K₂Cr₂O₇)(Na₂CrO₄)(CrO₃)(Jones reagent)
  
  • can’t use mild oxidant PCC which creates aldehydes/ketones from alcohol

Ketones can’t be further oxidized to carboxylic acids due carbonyl carbon having no bonds to hydrogen; would require breaking carbon-carbon bond, goes beyond ability of even strong oxidizing agents

Question 252

Reduction of aldehydes/ketones - nucleophilic addition

Answer 252

Aldehydes and ketones can be reduced to alcohols using hydride based reducing agents

• NaBH_4, LiAlH₄

Aldehydes/ketones also undergo nucleophilic addition reactions

• carbonyl oxygen gains a hydrogen to become (OH),
• nucleophilic attack by H₂O breaks double bond and adds water
  
  • newly added water is deprotonated, resulting in two (OH) groups
• Product is a geminal diol;

Same reaction with alcohol produces hemiacetal or hemiketal

• However, alcohol can continue to react and form acetal/ketal

Last addition reaction is with hydrogen cyanide, forms cyanohydrin

Question 253

Reduction of aldehydes and ketones - nucleophilic substitution

Answer 253

Imine formation: nucleophile is an amine and Nitrogen from amin replaces carbonyl oxygen

• carbon to nitrogen double bond

Question 254

Nucelophilic addition

Answer 254

Begin with nucleophilic attack, but no leaving group

1. Oxygen protonated
2. nucleophilic attack
3. deprotonation

Common examples of nucleophiles: water, alcohols, hydrogen cyanide

• all have a spare electron pair to donate

Question 255

Hemiacetal and hemiketal / acetal and ketal

Answer 255

Contain R group, OR group, OH group; hemiacetals have H group as well and hemiketals have second R group instead

Nucleophilic substitution of an alcohol to knock of hydroxyl groups and become acetal/ketal groups

Question 256

Substrate

Answer 256

the substance on which an enzyme acts

or

an underlying substance or layer; the surface or material on or from which an organism lives, grows, or obtains its nourishment

Question 257

Deprotonated aldehydes and ketones reactions

Answer 257

Alpha carbon functions as nucleophile,

ex. Aldol condensation: nucleophilic enolate of aldehyde or ketone attacks electrophilic carbonyl of another

Question 258

Carboxylic acids nomenclature

Answer 258

IUPAC: “-oic acid”, highest priority of any functional group

Common names:

• • acetic acid = ethanoic acid = vinegar
• • formic acid = methanoic acid
• COOH w/ cyclic compound = “-carboxylic acid” suffix
  
  • ex. cyclohexanecarboxylic acid
• Two = “-dioic acid”
  
  • butanedioc acid = succinate; important substrate in aerobic metabolism

Question 259

Carboxylic acid physical properties

Answer 259

Readily form hydrogen bonds which are stronger than alcohols

• Result in very strong intermolecular forces, high melting/boiling points
• Fairly acidic, hydroxyl group has pKa of 4-5
  
  • lower with electron withdrawing groups to stabilize conjugate base
  • **resonance stablized when OH is deprotonated, adds to acidity
  • Inductive effect by electron withdrawing groups increase acidity
    
    • diminishes w/ distance from COOH
    • alkyl groups have opposite effect; electron donating
• Like aldehydes and ketones, a-hydrogen is also weakly acidic
  
  • has renonance and creates enolates

Question 260

Acids are stronger when conjugate base is more stable because

Inductive effect

Answer 260

If an conjugate base is very stable and favors being in its base form, then it’s acid form is more willing to give up its proton

Question 261

Ranking compounds by acidity

Answer 261

1. Functional group acidity
2. Secondary characteristics: inductive groups and electron withdrawing groups

Question 262

Carboxylic acid biological reactions

Answer 262

Saponification: triglyceride + strong base (such as NaOH), TGC esters bonds are broken by nucleophilic attack

• forms carboxylate anions at the end of hydrocarbon chain
• anion forms salt with cation left behind by base (in this case Na)
  
  • used industrially to form soaps

Redox reactions:

• Reduced to alcohols with strong reducing agents(LiAlH₃)
• Reducing to aldehydes requires medium reducing agent (DIBAL-H) in equimolar ratio

Decarboxylation: carboxyl group lost as molecule of CO₂

• substrate usually 1,3-carboxylic acid
• favored at high temp and upregulated by decarboxylase enzymes
• Conversion of pyruvate to acetyl-CoA by pyruvate dehydrogenase complex for aerobic metabolism
• * also occurs in two reactions of citric acid cycle
• responsible for conversion of THCA to THC

Highly electrophilic carbonyl carbon allows for variety of nucleophilic substitution reactions, (OH) is good leaving group and replaced by nucleophile

• ammonia/amine creates amide
• esters formed by alcoholic nucleophile = FISCHER esterification
• acid anhydrides created by combining two carboxylic acids

Question 263

Fatty acids

Answer 263

Carboxylic functional groups attached to nonpolar hydrocarbon chain

Question 264

Hell-Volhard-Zelinsky Halogenation

Answer 264

Halogen added to carboxylic acid

Unlike other carboxylic acid reactions, uses alpha carbon

Bromination example:

1. Phosphorus tribromide and diatomic bromine
   
   1. Bromine replaces hydroxyl group = acyl halide
2. Keto-enol tautomerism yields enol version which reacts with diatomic bromine, bromine added to alpha carbon
3. Carboxylic acid reformed with bromine on alpha carbon

Question 265

Carboxylic acid derivatives

Answer 265

Esters, amides, acid anydrides

• derived by using appropriate nucleophile
• common in nature and industrialization
  
  • amids make up peptide bonds in aminos and proteins
  • low molecular weight esters common in fragrance industry, also responsible for pleasant aromas in fruits/oils
  • triglycerides are esters of glycerols and fatty acids
  • acid anhydrides used industrially to prepare acetate esters used for photography film and eyeglass frame

Derivatives closely reltaed and can be interconverted, ease of conversion depends on reactivity (determined by stability of leaving group and electrophilicity of carbonyl carbon; also have to consider steric hindrance)

• Carboxylates least reactive< amides< esters< carboxylic acids< esters< anyhydrides< acyl halides
• **can convert from less stable to more stable but not vice versa

Question 266

Amides (carboxylic acid derivative)

Answer 266

amides- amine instead of OH in COOH group

• primary, secondary, or tertiary depending on type of amine used to produce them
• suffix “-amide”; if using secondary or tertiary amide, substituents on nitrogen atom identified with “N”
  
  • ex. N-methyl-propanamide

More hydrogen substituents on Nitrogen leads to more H-bonding

• Means higher melting and boiling points
• More alkyl groups bonded to nitrogen means less H-bonding, lower melting/boiling points

Intermolecular forces weaker than alcohols/carboxylic acids

Weak bases, inert to acid base reactions because 1. carbonyl pulls electrons away from nitrogen and 2. resonance between them stabilizes the structure = less reactive

• carbonyl carbon is still electrophilic, allows some nucleophilic subs

Question 267

Lactams

Answer 267

lactams- cyclic amides

• alpha = alpha carbon closes ring; beta = beta carbon closes ring, gamma and delta
  
  • **beta: many drugs including broad spectrum antibiotics like peniccilin
    
    • four membered ring, experience high ring strain

Question 268

Esters (carboxylic acid derivative)

Answer 268

Can’t hydrogen bond = usually rather volatile; no acid base chemistry

Prone to acid/base catalyzed hydrolysis

IUPAC- two alkyl groups must be differentiated, one is bound to carbonyl group;

• “-oate” suffix given to carbonyl chain
• esterifying group (other chain) = “-yl”
  
  • ex. ethyl hexanoate

Question 269

Lactones

Answer 269

Cylcic esters, also use beta, gamma, and delta (depending on which carbon closes the ring)

Question 270

Acid anhydrides (Carboxylic acid derivative)

Answer 270

Two carboxylic acids stuck together through condensation reaction

symmetric= replace “acid” in carboxylic acid with anhydride (ex. acetic anhydride)

asymmetric= name chains in alphabetic order (ex. butanoic ethanoic anyhydride)

Question 271

Acyl halides (carboxylic acid derivative)

Answer 271

Reacting carboxylic acid with halogenated reagent

• can’t form hydrogen bonds, low boiling point
• however, extremely reactive
  
  • halides excellent leaving groups

Question 272

Carboxylate

Answer 272

Carboxylic acid anion

• resonance stabilized, unlikely to form good leaving group

Question 273

Transesterification

Answer 273

Ester reacts with alcohol (has to be different from alcohol used to form the ester)

• new alcohol replaces esterifying group, results in new ester and new alcohol

Question 274

Acid catalyzed amide hydrolysis

Answer 274

Molecule of water adds across amid bond, generating an amine and a carboxylic acid

• through this process that peptide bonds are broken in proteolysis

Enzymes called proteases/peptidases catalyze reaction, often specific between amino acids

Question 275

life on earth began 3.8 b.y.a

Answer 275

Earth atmosphere had no oxygen for 1.8 b.y.

Many organisms don’t require oxygen, and our oxygen requiring metabolic pathways use anaerobic pathways

Question 276

Glycolysis (aerobic vs. anaerobic cells)

Answer 276

Metabolic process common to all cells on earth; obtains energy from glucose regardless if oxygen is present. Doesn’t provide that much energy

• in cells that can use oxygen, other metabolic processes provide most of cell’s energy needs; glycolysis sufficient for simple anaerobic cells

In aerobic cells, glycolysis provides starting point for glucose breakdown and can serve as energy in conditions insufficient oxygen is present

Question 277

Where does glycolysis occur?

Answer 277

Cytosol of cell

Question 278

3 things to account for in glycolysis

Answer 278

1. One molecule of glucose –> 2 pyruvate (3-carbon alpha-keto acid)
   
   1. pyruvate has two carbonyls, glucose 5 hydroxyl groups == redox reactions
   2. 6 carbon glucose broken down into two 3 carbon molecules
2. Two NAD+ + 2H+ –> 2 NADH
   
   1. electron carriers which store energy
3. two ADP + 2 P_i –> 2 ATP (for every one glucose molecule)
   
   1. adding inorganic phosphate group to ADP

Question 279

What pathways is pyruvate involved in?

Answer 279

• Citric acid cycle (aerobic respiration)
• Lactate fermentation (anaerobic respiration)
• Gluconeogenesis (during high ATP/ADP ratio)
• Fatty acid synthesis (energy storage)

Question 280

Isomerase (enzyme)

Answer 280

Converts between two isomers

ex. glucose 6-phosphate isomerase converts between glucose and fructose (structural isomers)

Question 281

Glycolysis number of steps and subdivisions

Answer 281

10 steps: energy investment phase first (5 steps) and energy payoff phase second (also 5 steps)

energy investment: cell spends 2 ATP to power several energetically unfavorable reactions

• glucose enters cell through glucose transporters (so it can’t escape if extracellular glucose gets too low)

energy payoff phase: 4 ADP to 4 ATP (gains more than spent), gain of 2 ATP per glucose molecule

Question 282

Energy investment steps of glucose

Answer 282

1. glucose enters cell through glucose transporters and enxyme hexokinase adds phosphate group = 6GP
   
   1. costs an ATP, traps glucose in cell (puts -2 charge on glucose, making it polar; also reduces glucose conc in cell, allows cell to pull in more glucose)
2. Enzyme glucose 6-phosphate isomerase converts G6P to F6P ​(fructose 6-phosphate)
   
   1. name of enzyme tells us whats happening
3. F6P converted to F1,6BP (fructose-1,6-biphosphate) by phosphofructokinase-1
   
   1. ​adds second phosphate group to substrate, another energy investment step
   2. ***most important step of glycolysis, no turning back point
      
      1. committed, rate-limiting step
      2. **highly regulated
4. F1,6BP cleaved into G3P and DHAP (glyceraldehyde 3-phosphate and dihydroxyacetone phosphate)
   
   1. catalyzed by aldolase
5. Converts DHAP to another G3P catalyzed by triosephosphate isomerase
   
   1. want to have two identical molecules for next steps

Added two phosphate groups and broke molecule in half to end up with 2 G3P –> ready for energy payoff phase

Question 283

Energy payoff steps of glycolysis (starts with step 6)

Answer 283

*** Each step happening twice, one for each molecule of G3P (twice for each molecule of glucose)

1. G3P to 1,3-biphosphoglycerate (1,3PG) catalyzed by GADPH (G3P dehydrogenase) (redox reaction)
   
   1. creates a NADH from NAD+ and adds another phosphate
   2. Doesn’t require ATP because NAD+ production highly exergonic, which enzyme uses to add inorganic phosphate (substrate-level phosphorylation)
2. 1,3PG to 3-phosphoglycerate (3PG) by phosphoglycerate kinase (PGK)
   
   1. one phosphate group pulled off to generate an ATP
   2. regulated step
3. Phosphogylcerate mutase converts 3PG to 2PG (phosphate group moved over)
4. Enolase turns 2PG to PEP (phosphoenolpyruvate)
5. enzyme pyruvate kinase converts PEP to pyruvate, removes remaining phosphate group making another ATP
   
   1. regulated

2 molecules of G3P produce 1 pyruvate each, 2 ATP each, and 1 NADH

Used two ATP, net gain two ATP

Question 284

Substrate-level phosphorylation

Question 285

What can we do with products of glycolysis?

Answer 285

2 ATP, 2 NADH, and 2 pyruvate molecules

2 molecules of ATP can be used for energy

If cell can use aerobic respiration, NADH to electron transport chain to produce even more ATP

• pyruvate undergoes further modifications for citric acid cycle to make more ATP

In an anaerobic cell or under anaerobic conditions, need to regenerate NAD+ to keep glycolysis cycle going

• pyruvate and NADH undergo fermentation to do so

Question 286

Why glucose need to be regulated?

Answer 286

If already have plenty of energy, burns glucose that can be stored and used when you need energy more.

also, cell would use up all NAD+, then get stuck in step 6 of glycolysis when it is required

• unable to convert G3P into 1,3PG
• why cells need electron transport chain or fermentation

Glycolysis is upregulated when cell needs ATP, and downregulated when cell has enough

Question 287

In what type of cells is glycolysis strongly upregulated?

Answer 287

Cancer cells

Question 288

How does the cell sense energy balance? (for glycolysis)

Answer 288

cell senses relative concentrations of ATP compared to ADP and AMP (byproducts of use of ATP for energy)

• low ADP and AMP compared to ATP means cell has enough energy
• high ADP and AMP and low ATP means cell is low on energy

High citrate and high NADH levels also signal cell doesn’t need energy through glycolysis

• citrate important intermediary of CAC and NADH product of CAC and glycolysis
  
  • indicators cell has enough materials to make ATP

***end products inibiting what made them = negative feedback regulation

Question 289

What hormones regulate glycolysis

Answer 289

Hormones insulin and glucagon

• insulin upregulates glycolysis
  
  • Insulin inhibits fructose 2,6-bisphosphatase and activates PFK-2, increasing fructose 2,6-bisphosphate which activates PFK-1 and stimulates glycolysis (committed step)
    
    • insulin levels are high when blood sugar levels are high, want to be able to break down glucose and harness its energy
• glucagon downregulates it
  
  • Glucagon activates fructose 2,6-bisphosphatase and inhibits PFK-2 (two components of bifunctional enzyme), reducing fructose 2,6-bisphosphate which downregulates PFK-1 preventing glycolysis (committed step)
    
    • Makes sense because glucagon levels high when blood sugar levels are low, don’t want to use up that glucose
      
      • want to liberate it into bloodstream for other cells to use

One of insulins job is to get glucose into the cell

One of glucagons job is to get liver cells to produce glucose to push out into the bloodstream (gluconeogenesis)

Question 290

1st regulatory step of glycolysis

Answer 290

• First step of glycolysis when hexokinase turns glucose into glucose 6-phosphate
  
  • Prevents glucose from leaving the cell, however G6P is not committed yet (can enter glycogenesis and pentose phosphate pathway)
  • G6P inhibits hexokinase, therefore prevents cell from making too much of itself

Liver and pancreatic cells contain special version of hexokinase called glucokinase, which has a lower affinity for glucose and isn’t regulated by G6P

• Allows liver and pancreatic cells to respond to amount of glucose in environment rather than demand for G6P and ATP in the cell
• Important because liver and pancreas have system wide functions in the body

Question 291

What does liver do

Answer 291

Stores and releases glucose as glycogen for other body tissues

• liver cells needs to store and absorb more glucose than needed for their metabolic needs

Question 292

2nd regulatory point in glycolysis

Answer 292

Committed step: 3rd step when phosphofructokinase-1 (PFK-1) creates fructose 1,6-biphosphate from F6P

Enzyme PFK-1 is downregulated by high levels of ATP and citrate, which indicate cell has enough energy

• upregulated when cell has too much ADP

Also regulated at organism wide level by insulin and glucagon:

• PFK-1 allosterically regulated by fructose 2,6-phosphate (molecule solely responsible for this regulation)
• activates PFK-1 to extent that glycolysis stops without it

Fructose 2,6-phosphate produced and broken down by single bifunctional enzyme with two components:

1. phosphofructokinase-2 (PFK-2) = creates fructose 2,6-bisphosphate
2. fructose 2,6-bisphosphatase = breaks down fructose 2,6-biphosphate

Glucagon activates fructose 2,6-bisphosphatase and inhibits PFK-2, reducing fructose 2,6-phosphate and downregulating PFK-1 glycolysis

• Makes sense because glucagon levels high when blood sugar levels are low, don’t want to use up that glucose
  
  • want to liberate it into bloodstream for other cells to use

Insulin inhibits fructose 2,6-bisphosphatase and activates PFK-2, increasing fructose 2,6-bisphosphate which activates PFK-1 and stimulates glycolysis (committed step)

• insulin levels are high when blood sugar levels are high, want to be able to break down glucose and harness its energy

Question 293

Kinases (enzymes)

Answer 293

Add phosphate groups to their substrates

Question 294

Phosphatases (enzyme)

Answer 294

Remove phosphate groups from substrates

Question 295

3rd regulatory step in glycolysis

Regulated by?

Answer 295

Final 10th step, phosphoenolpyruvate (PEP) is converted into pyruvate by enzyme pyruvate kinase

• Pyruvate kinase is allosterically inhibited by ATP
  
  • if theres a lot of ATP in the cell, final reaction is inhibited

Pyruvate kinase is also inhibited by acetyl-CoA

• which is derived from pyruvate and long-chain fatty acids, also metabolized for energy

Question 296

Allosteric inhibition

Answer 296

Allosteric regulation is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme’s active site

(add picture)

Question 297

What mechanisms regenerate NAD+ needed for step 6 of glycolsis?

Answer 297

Aerobic respiration: electron transport chain

Anaerobic respiration: fermentation

Parallel pathways

Question 298

Lactic Acid Fermentation

Answer 298

Occurs in anaerobic cells that never use oxygen and aerobic cells that don’t have access to oxygen for period of time

ex. muscle cells carry out lactic acid fermentation in high intensity exercise; not getting enough O₂ and relying on glycolysis

mechanism: single redox reaction where lactate dehydrogenase converts pyruvate to lactic acid

• simultaneously, NADH is oxidized to NAD+ to go back into glycolysis

Fermentation itself doesn’t make any ATP

Question 299

Ethanol fermentation

Answer 299

Much less common among eukaryotes but famously carried out by yeasts (single celled eukaryotes) – converts sugars into ethanol

• how alcoholic beverages like beer, kimchi, yogurt are made

1. Starts with glucose or disaccharide like sucrose (glucose attached to fructose)
   
   1. Gets converted to pyruvate through glycolysis (same process so far)
   2. Then enzyme pyruvate decarboxylase converts pyruvate into acetaldehyde, carbon lost as molecule of CO₂
2. Alcohol dehydrogenase turns acetaldehyde into ethanol while NADH is oxidized into NAD+ (feeds back into glycolysis)

Question 300

How can you obtain glucose?

Answer 300

Body can obtain glucose by eating, by breaking down stored glucose - glycogen, or by gluconeogensis

Question 301

What does gluconeogenesis do and how does it begin?

Answer 301

Gluconeogenesis creates glucose from other biochemical substrates, occurs mainly in the liver (and to a lesser extent in the kidneys)

• Begins with pyruvate from
  
  • protein (glucogenic amino acids = not leucine or lysine)
  • glycerol = product from fatty acid breakdown
  • lactate from lactic acid fermentation

Question 302

Gluconeogenesis 1st bypass step (also first step)

Answer 302

Looks like glycolysis in reverse but glycolysis has 3 irreversible steps:

1. Pyruvate to PEP takes two steps instead of one in the reversible reaction (10th step of glycolysis); occurs in mitochondria (***to avoid pyruvate from glycolysis being converted back into PEP)
   
   1. Enzyme pyruvate carboxylase converts pyruvate into oxaloacetate
      
      1. Oxaloacetate briefly converted to malate to be transported out of mitochondria into cytosol then converted back into oxaloacetate
   2. PEP carboxykinase converts it into PEP

Then, follows reverse of glycolysis until has to use enzymes to bypass steps of glycolysis that require ATP input

Question 303

Gluconeogenesis second, third, and fourth bypass steps (last three steps)

Answer 303

8. Fructose 1,6-bisphosphate (product of committed step of glycolysis that requires ATP) is converted to fructose 6-phosphate by enzyme fructose 1,6-bisphophatase (hydrolyzes a phosphate group)
9. Fructose 6-phosphate converted into G6P by phosphohexose isomerase (same enzyme from glycolysis)
10. Glucose 6-phosphate converted back into glucose by glucose 6-phosphatase (hydrolyzes another phosphate group)

*** only two different steps from glycolysis

Once liver has newly formed glucose, send it out into bloodstream increasing blood glucose conc and for other cells to utilize

Question 304

Cells capable of performing both glycolysis and gluconeogenesis

Answer 304

Liver and kidney cells, regulate processes so one predominates at a given time

Question 305

Gluconeogenesis and insulin/glucagon

Answer 305

Like glycolysis, regulated by insulin and glucagon (regulate blood glucose levels in general)

• Insulin- promotes glycolysis, inhibits gluconeogenesis
  
  • secreted when blood glucose is high
  • promotes synthesis of fructose 2,6-bisphosphate
• Glucagon- inhibits glycolysis, promotes gluconeogenesis
  
  • secreted when blood glucose is low
  • reduces amount of fructose 2,6-bisphosphate incell (inhibitor of fructose 1,6-bisphosphatase/gluconeogenesis)

Question 306

Regulation of gluconeogenesis

Answer 306

Occurs at steps where gluconeogenesis bypasses the irreversible steps of glycolysis; only need to focus on two

• First step - 2 step pyruvate to PEP through oxaloacetate
  
  • cell has choice - push pyruvate through gluconeogenesis to make glucose or through mitochondria/aerobic respiration to make ATP
    
    • to make energy, converts pyruvate into acetyl CoA in mito
    • acetyl CoA regulates gluconeogenesis this way; if there’s plenty, downregulates conversion of pyruvate into acetyl CoA
      
      • causes pyruvate to build up in cell and go to gluconeogenesis
• • 9th step (fructose 1,6-bisphosphate to fructose 6-phosphate by enzyme fructose 1,6-bisphosphatase)
    
    • committed and rate limiting step of glycolysis
    • step where balance between gluconeogenesis and glycolysis is maintained
    • • Fructose 1,6-bisphosphatase enzyme is inhibited by AMP
        
        • high levels of AMP signal the cell is low on energy –> glycolysis
    • In addition, regulatory compound fructose 2,6-bisphosphate also inhibits fructose 1,6 bisphosphatase enzyme
      
      • *** high levels of fructose 2,6-bisphosphate activate glycolysis and inhibit gluconeogenesis

Question 307

Mitochondria structure

Answer 307

Double membrane - two separate lipid bilayers with space between them

Inner and outer mitochondrial membrane

Intermembrane space in between them

Mitochondrial matrix is innermost region in inner mito membrane

Question 308

Outer mitochondrial membrane

Answer 308

Highly porous, studded with membrane proteins called porins which allow hydrophillic molecules and even ions to move freely in and out by diffusion

Question 309

Inner mitochondrial membrane

Answer 309

impermeable to almost everything but water and small gas molecules (oxygen and carbon dioxide)

• larger molecules can only enter through special transport proteins
• has incredible surface area; 5x as large as outer membrane
  
  • has to be folded, folds are called cristae

Also contains embedded proteins of the Electron Transport Chain (produce most of cell’s ATP)

Question 310

Intermembrane space (mitochondria)

Answer 310

Compartment tends to be acidic due to protons being pumped from innermost region into intermembrane space

Question 311

Mitochondrial matrix

Answer 311

Innermost region, contains:

• citric acid cycle enzymes
• electron carriers
• mitochondrial RNA and DNA
• ribosomes

Question 312

Metabolism in aerobic cells

Answer 312

1. Glucose broken down into pyruvate by glycolysis
2. Pyruvate enters mito matrix by pyruvate dehydrogenase complex
3. Pyruvate converted into acetyl CoA in mitochondria
4. Acetyl CoA enters the Citric Acid Cycle (Krebs/TCA (tricarboxylic acid))
   - Citric Acid Cycle not just next step after glycolysis, but crossroads for other metabolic pathways; non-carbohydrate precursors can get fed into it at certain steps and its intermediates can go take part in other anabolic process
5. Citric Acid Cycle produces reduced electron carriers NADH and FADH₂ which are used to produce energy in oxidative phosphorylation

Question 313

Pyruvate Dehydrogenase Complex

Answer 313

Embedded in inner mitochondrial membrane

• Converts pyruvate –> acetyl CoA by decarboxylation (oxidation) as pyruvate crosses inner mito membrane
• also produces one NADH (corresponding reduction)

3 different enzymes physically linked together so their reactions happen efficiently and in sequence

1. Pyruvate dehydrogenase
2. Dihydrolipoyl transacetylase
3. Dihydrolipoyl dehydrogenase

Also requires help from 5 coenzymes: thiamine pyrophosphate, FAD, NAD, Coenzyme A, and lipoate

Produces two NADH per glucose

Question 314

decarboxylation

Answer 314

Removal of a carboxylic acid group

Question 315

What is acetyl CoA

Answer 315

Two carbon compound linked through a sulfur atom to larger molecule coenzyme A-

Involved in pyruvate dehydrogenase complex,

• Derived from fatty acid oxidation and the breakdown of certain amino acids

Main entry point of Citric Acid Cycle

Question 316

Citric Acid Cycle basics

Answer 316

Citric Acid Cycle not just next step after glycolysis, but crossroads for other metabolic pathways; non-carbohydrate precursors can get fed into it at certain steps and its intermediates can go take part in other anabolic process

Generates some ATP directly through production of GTP, main goal is to produce reduced electron carriers NADH and FADH₂ – used later to produce energy through oxidative phosphorylation

Called a cycle because it regenerates the compound it starts with, can continue steps as long as acetyl CoA is inputed

Question 317

Where does Citric Acid Cycle occur?

Answer 317

• in aerobic prokaryotes with no mitochondria, Citric Acid Cycle occurs in cytoplasm; in eukaryotes, takes place in mitochondrial matrix

Question 318

Citric Acid Cycle steps

Answer 318

• Acetyl CoA joins with 4-carbon oxaloacetate to form 6-carbon citrate
  
  • citrate undergoes redox and decarboxylation reactions to form products of CAC
• Final product is oxaloacetate, joins with acetyl CoA to start process again

1. Acetyl CoA joins with oxaloacetate to form citrate (deprotonated form of citric acid)
   
   1. reaction catalyzed by citrate synthase; energetically favorable/irreversible
2. Citrate converted to cis-Aconitate and then Isocitrate by enzyme aconitase
   
   1. ​reversible, moves hydroxyl group
3. Isocitrate converted to oxalosuccinate and then a-ketoglutarate
   
   1. enzyme isocitrate dehydrogenase
   2. **releases CO₂ (first carbon lost)(one reason we exhale carbon dioxide as waste)
   3. One molecule of NADH produced; rate-limiting and irreversible
4. a-ketoglutarate converted into succinyl CoA by a-ketoglutarate dehydrogenase
   
   1. **also produces one NADH and loses one CO₂
   2. have lost both acetyl CoA carbons
5. Succinyl CoA converted to succinate by
   
   1. succinyl-CoA synthetase
   2. produces molecule of GTP through substrate level phosphorylation
6. Succinate converted into fumarate
   
   1. ​by enzyme succinate dehydrogenase
   2. produces FADH₂
7. Fumarate oxidized by fumarase into malate
8. Malate is recycled back into oxaloacetate by malate dehydrogenase
   
   1. ​produces one more NADH
   2. thermodynamically unfavorable but progresses due to Le Chateliers principle because oxaloacetate is used up quickly

Question 319

Citric Acid Cycle products

Answer 319

Products are per pyruvate, double them to get products per glucose:

Per pyruvate:

From pyruvate dehydrogenase complex: 1 NADH

From citric acid cycle:

1 GTP (can be used directly as energy)

3 NADH

1 FADH₂

2 CO₂ (waste product)

Question 320

Electron transport chain (what it consists of, what it does, what it produces)

Answer 320

Consists of 4 membrane bound protein complexes (I, II, III, IV) located on innermembrane in eukaryotes

Harvest electrons from electron carriers NADH and FADH₂ in a set of reactions that also pumps H+ into mitochondrial intermembrane

• uses electrons to drive production of energy in form of ATP via oxidative phosphorylation
• electrons ultimately converted to water via redox reaction

Question 321

Oxidative phosphorylation (what it’s used for, steps)

Answer 321

Used in mitochondria for forming ATP

1. Electron transport chain pumps H+ into inter membrane space of mitochondria
2. H+ diffuse down concentration gradient into matrix powering ATP synthase (embedded in inner membrane, synthesizes ATP)
3. Electrochemical energy stored in charge differential between inter membrane space and matrix produces ATP

Question 322

Per glucose molecule… (products through all metabolic processes)

Answer 322

2 ATP from glycolysis; 2 NADH

0 ATP from PDC, 2 NADH

2 GTP from citric acid cycle; 6 NADH; 2 FADH2

(10 NADH x 2.5 ATP) + (2 FADH2 x 1.5ATP) = 28 ATP from oxidative phosphorylation

32 ATP total per glucose but had to use 2 ATP to get pyruvate from cytoplasm so really 30 ATP

Question 323

In aerobic prokaryotes, electron transport chain protein complexes are located…

Answer 323

In cell membrane

Question 324

Electron transport chain complex reduction potentials

Answer 324

Each electron carrier (I, II, III, IV) has more positive reduction potential than the one before it - series of redox reactions

• more positive reduction potential means compound wants to be reduced more (wants electrons more, keeps them moving consistently)
• as electrons pass from carrier to carrier, energy is used to pump protons across inner membrane into matrix producing proton gradient used to power oxidative phosphorylation
• ends with oxygen, final electron acceptor, has highest reduction potential in ETC
• picks up two protons and is turned into molecule of water x2
• ** why aerobic respiration requires oxygen

Summarize ETC as set of redox reactions that transfer electrons from NADH and FADH₂ to O_2, reducing it to water

H’s from NADH and FADH2 are broken off as H+ protons and electrons

Question 325

Two different pathways electrons can take through ETC: NADH pathway

Answer 325

1. NADH from glycolysis, PDC, and CAC drops off two electrons at complex I (NADH dehydrogenase) -> NAD+
2. Electrons transferred to electron carrier ubiquinone, reducing it to ubiquinol
   
   1. ubiquinone = ketone, ubiquinol = alcohol
3. Energy from this reaction harnessed by complex I to send 4 protons (H+) across the matrix into intermembrane space
4. Ubiquinol bypasses complex II and transfers electrons to carrier cytochrome C, which can only carrier one electron - so theres two cytochrome C’s
   
   1. (hemeprotein, core component is Fe, alternates between Fe+2 and Fe+3)
5. During which, complex III sends four more H+’s into intermembrane space
6. Ends at complex IV which pumps two H+’s, where cytochrome C’s transfer electrons to oxygen reducing it to water

Question 326

FADH₂ electron transport chain pathway

Answer 326

Each acetyl CoA through CAC gives rise to one FADH₂ which remains connected to enzyme that produced it, succinate dehydrogenase which is also complex II of ETC

• important point of overlap between CAC and ETC
• electrons from FADH2 enter at complex II instead of complex I

Complex II doesn’t pump any protons into intermembrane space, means less ATP can be generated than from NADH (1 NADH ~ 2.5 ATP, 1 FADH2 ~ 1.5 ATP)

Otherwise, path is the same as electrons after they go through complex I from NADH

Question 327

Proton motive force

Answer 327

Proton gradient created from protons being pumped out of matrix into intermembrane space

Entrapped protons want to move back into matrix to dissipate their charge and concentration gradient = stored electrochemical energy

• However, inner membrane is impermeable to ions, have to reenter through ATP synthase
  
  • uses flow of protons to power formation of ATP from ADP and inorganic phosphate (P_i)

Question 328

Why would we need regulation of aerobic respiration (CAC and ETC)

Answer 328

Already have plenty of ATP available or not enough oxygen available; lots of ADP upregulates

Question 329

Where does regulation of aerobic respiration occur

Answer 329

CAC and ETC work simultaneously

If plenty of energy, best way to downregulate is at the entry point to prevent both processes from happening = at pyruvate dehydrogenase complex (PDC)​

Regulation can also occur in 3 steps of Citric Acid Cycle

Question 330

Upregulation of aerobic respiration

Answer 330

When there are high levels of coenzyme A, AMP, and NAD+, indicates cell needs more energy and PDC is upregulated to produce more acteyl CoA

Question 331

Downregulation of aerobic respiration

Answer 331

• When cell has high levels of ATP, NADH, and acetyl CoA it downregulates PDC
  
  • feedback inhibition
• • High levels of fatty acids can also downregulate PDC
    
    • fatty acids metabolized into acetyl CoA

Question 332

Regulation in Citric Acid Cyle (respiration regulation)

Answer 332

3 key steps regulated:

1. First step when acetyl-CoA and oxaloacetate combine to form citrate upregulated by ADP, downregulated by ATP and NADH
   
   1. also inhibited by citrate and succinyl-CoA, intermediates downstream of reaction
2. Conversion of isocitrate to alpha-ketoglutarate is downregulated by ATP, upregulated by ADP
3. Formation of succinyl-CoA is inhibited when cell has too much succinyl-CoA or too much NADH

**Pattern - energy production steps upregulated by compounds that suggest cell needs more energy, downregulated by cells that indicate cell has enough

Question 333

Disruption of Cellular Respiration processes

Answer 333

Several drugs and toxins interfere with electron transport chain

ex. cyanide inhibits cytochrome C oxidase, enzyme that transfers electrons to oxygen, shuts ETC down

Can be fatal

Question 334

Quantitative experimental methods

Answer 334

Generate numerical data

• always produce numbers as results
• categorized, ranked, or used to construct graphs and draw statistical conclusions

Question 335

Qualitative experimental methods

Answer 335

Not numbers; words, opinions, observations, anything not numerical

• more open-ended, exploratative
• cannot be easily quantified

Usually when there’s not much prior research on a topic

Question 336

Mixed research methods

Answer 336

Mix of both qualitative and quantitative methods

• ask participants to eat a certain number of donuts, then describe their feelings

Question 337

Objective experimental measures

Answer 337

Unbiased

Fact-based

ex. height

Question 338

Subjective experimental measures

Answer 338

Subject to opinion

No right or wrong answer

ex. how comfortable do you feel right now

Question 339

Validity

Answer 339

The extent to which a studys results are both genuine and generalizable

1. How do we know results are accurate?
2. How do we know that our results will apply to the “real world” rather than being specific to that experiment?

Accurate results

Question 340

Internal validity

Answer 340

Draw causal conclusions - minimize confounding variables

manipulating X caused a change in Y

confounding variable- outside factor not being study that impacts both variables

• can lead to incorrect conclusions

Question 341

External validity

Answer 341

Extent we can generalize results (to different experimental realizations or real life)

Question 342

Test validity (4 types)

Answer 342

Tests what it intended to

• construct validity- assesses construct designed to test
• content validity- how well test covers full scope of content intended to measure
• criterion validity- how well test correlates with well-respected criterion
• predictive validity- focuses on future events

Question 343

Reliability

Answer 343

Extent to which study results are consistent when repeated

• if we do same study over again, is there a positive correlation between them

Question 344

Precision

Answer 344

The extent to which experimental measurements agree

• Refers to data points

Question 345

Accuracy

Answer 345

The extent to which measurements agree with standard/correct values

• Data points
• Validity

Question 346

4 experimental study scenarios

Answer 346

1. Reliable and valid- experiment yields consistent values close to the true value
   
   1. ideal scenario
2. Unreliable and invalid- repeating the experiment yields inconsistent values
   
   1. results not close to true value
3. Reliable and invalid- data points clustered closely around an inaccurate value
4. Unreliable and valid- results all over the place but average is close to true value

Question 347

Reliability and validity

Answer 347

Characteristics of a study

Question 348

Precision and accuracy

Answer 348

Characteristics of a data set

Question 349

Survey methods

Answer 349

• Collect large amounts of data
  
  • • Often take form of questionnaires
  • • Participants must be representative of population intended to study
  • • Normally inexpensive and easy to implement; can reach large sample
  • • **Problems can arise from bias

Question 350

Questionnaires

Answer 350

Form of self report - participant responds without interference

• Often use Likert scales- statement followed by continuum of possible responses (ex. from 1-5, strong disagreement to strong agreement)

Question 351

Self-reporting bias (survey methods)

aka Response bias

(two types)

Answer 351

Bias inherent to survey method; natural side effect of allowing participants to choose their responses

• social desirability bias- answer in a way that makes oneself appear more successful
• acquiesence bias- tendency to answer yes when asked a question, especially when uncertain
  
  • can counter by including survey items with opposing meanings

Question 352

Mutations and how they can arise

Answer 352

Mistakes in DNA coding; can affect corresponding mRNA and by extention amino acid sequence and protein final product

• can arise when a cell is exposed to a DNA-damaging agent, or mutagen

- some can be deleterious and some can be beneficial, driving evolution

Question 353

Mutagens

Answer 353

DNA-damaging agent; not always harmful

• physical mutagens- heat and radiation
  
  • ionizing radition
  • UV light
• chemical mutagens- base analogs
  
  • ​reactive oxygen species (ROS)
• biological agents- viruses, bacteria, transposons

(add more to this)

Question 354

Common examples of reactive oxygen species

Answer 354

Peroxide, superoxide, hydroxyl radical

Contain lone electrons which make them especially reactive (would much rather exist in pairs)

Question 355

Spontaneous mutations

Answer 355

Occur in cells not exposed to mutagenic agents

ex. mistakes in DNA replication

Question 356

Base pair substitution mutation and 3 potential effects

Answer 356

Bases substituted for one another

• can impact at most one codon and therefore one amino acid

3 potential effects:

• silent mutation- no effect on amino acid sequence
• missense mutation- replaces an amino acid
• nonsense mutations- creates a stop codon

Question 357

Insertion/deletion mutation

Answer 357

Bases inserted into sequence (one or more) or bases deleted from sequence (one or more)

• can cause frameshift mutation: can change every subsequent codon in a sequence
  
  • if number of bases inserted or deleted is a multiple of three, reading frame won’t shift

Question 358

Silent mutations

Answer 358

Don’t change organisms phenotype

• genetic code degeneracy: multiple codons can code for same amino acid

Question 359

Missense mutations (2 types)

Answer 359

Amino acid is changed when DNA sequence is translated

• conservative- new amino acid has similar structure to old, partially conserve original function
  
  • ex. threonine to serine
  • minimal effects
• nonconservative- replaces original amino acid with one with very different structure
  
  • threonine to proline
  • can greatly impact final protein

Question 360

Nonsense mutations

Answer 360

Codon for an amino acid replaced with a stop codon; either UGA, UAA, or UAG

• truncates (shortens) protein, typically rendering it nonfunctional

Question 361

Pyrimidine dimer mutation

Answer 361

UV light; cytosine or thymine bases on SAME strand bind together

Question 362

Point mutations

Answer 362

Change to a single nucleotide

Can be subsitution, insertion or deletion

Question 363

Loss of function mutations

Answer 363

Partially or entirely prevent a protein from functioning correctly

Question 364

Gain of function mutation

Answer 364

Protein takes on new function that it didn’t have prior to mutation

Question 365

Chromosomal abnormalities (6)

Answer 365

Deletion, duplication, inversion, insertion, translocation, aneuploidy

• Deletion, duplication, and inversion take place on single chromosome
• Translocation and insertion tend to impact two chromosomes

Question 366

Chromosomal deletion

Answer 366

Removal of a segment of genes on a chromosome

• makes chromosome shorter
• what happens when a gene is deleted depends on allele on other chromosome
  
  • depends on genotype
    
    • ex. two alleles for brown hair color, if one gets deleted, may result in no change but transcribe less mRNA and make less protein corresponding to this hair pigment
    • if alleles are different, could change hair color

Question 367

Chromosomal duplication

Answer 367

Segment of a chromosome is copied; two copies of one allele on same chromosome

• generally results in more mRNA and protein corresponding to genes on duplicated segment

Question 368

Chromosomal inversion

Answer 368

Reversal in directionality of segment of DNA on chromosome

• unlike duplication and deletion, doesn’t change gene dosage
• many have no noticeable effects

Question 369

Chromosomal insertion

Question 370

Chromosomal translocation

Answer 370

Genetic material from one chromosome is exchanged with genetic material from another

• balanced transloaction- doesn’t result in lost or extra genes
  
  • typically harmless
  • ​may produce gametes with imbalances in the genetic material present which can cause child to have unbalanced translocation
• unbalanced translocation- results in lost or extra genes

Question 371

Chromosomal insertion

Answer 371

One way transfer- part of a chromosome breaks off and inserts itself in sequence of second chromosome

Question 372

Chromosomal transposition

Answer 372

Transposons- noncoding genetic elements that can initiate their own movement from chromosome to chromosome

• over 40% of human genome
• generally not problematic unless they insert in coding sequence of a gene
  
  • don’t translocate since movement is one way

Question 373

Chromosomal aneuploidy

Answer 373

Abnormal number of copies of a chromosome within a cell

• typical human cells have 23 pairs of chromosomes
• 22 autosomes and one sex chromosome pair

trisomy- extra copy of a chromosome

• trisomy 21- down syndrome

monosomy- one copy of a chromosome

**Typically results from nondisjunction, failure of chromosomes to segregate during anaphase of meiosis or mitosis

• risk increases with maternal age (older eggs)

Question 374

DNA repair

Answer 374

1 error per 1 billion bases - 6 billion base pairs per cell = ~6 errors per DNA replication

DNA polymerase proof reading- mistakenly added base becomes paired with a non-complimentary base on opposing strand

• hydrogen bonding between mismatched bases is unstable; detected by DNA pol
• removes base pair and reinserts correct base

also known as 3’-5’ exonuclease activity

Question 375

Mismatch repair

Answer 375

If DNA polymerase misses an error while proofreading

Immediately after DNA replication and through G2 stage, excision of base occurs

• base is party of newly replicated strand, so mismatch repair can distinguish new from old by DNA methylation

Functions only during replication

Question 376

Base excision repair

Answer 376

Removes a single erroneous base, limited to small scale errors

** non replicative errors

Question 377

Nucleotide excision repair

Answer 377

Removes multiple bases, can fix larger mutations

• ex. pyrimidine dimers

Question 378

Biological signals

Answer 378

Chemical- how cells respond to surrounding, communicate with other cells, and alter their own internal environments

Electrical

Mechanical

Question 379

Biochemical signals

Answer 379

How cells respond to surrounding, communicate with other cells, and alter their own internal environments

• hormones
  
  • peptide, steroid, or amino acid-derived molecules
    
    • travel through circulatory system to exert effects on target cells
• cytokines
  
  • ​small proteins that modulate immune responses
• neurotransmitters
  
  • ​chemicals that transmit information between neurons

Question 380

Biochemical classes

Answer 380

• Lipids
• Amino acids
• Proteins
• Gases
  
  • neurotransmitter nitric oxide

Question 381

Types of Signaling

-crine

Answer 381

Differentiate terms by how far they travel through the body

• intracrine signals travel the shortest distance
  
  • signals act within the cell that synthesizes them
• autocrine signals are released, then bind to receptors on the cell that synthesized them
• juxtacrine
  
  • ​signals travel between cells in close contact
• paracrine
  
  • ​signals travel between nearby cells

endocrine- signals (hormones) travel between distant cells via circulatory system

Question 382

Sugar consumption promotes release of

Answer 382

Insulin, a hormone that is an endocrine signal

Question 383

Inflammation involves the release of

Answer 383

Cytokines; affect nearby cells via paracrine signaling

• cells respond to fight infection or promote wound healing

Question 384

Cocaine use affects…

Answer 384

Release and reuptake of multiple neurotransmitters (also technically paracrine signalling molecules; secreted by one neuron and act on a neighboring neuron)

Question 385

When signaling molecule binds to a receptor, it is a…

When it binds to the receptor, it triggers…

Answer 385

Ligand

An action that affects the target cell

Question 386

First messengers

Second messengers

Answer 386

Ligand (signal molecule) that binds to receptor on cell surface, initiates signaling pathway

Receptor triggers release of another biosignal in the cell

• common secondary messengers are calcium ions and cyclic adenosine monophosphate (cAMP)

Question 387

Types of receptors

Answer 387

Membrane receptors- attached to plasma membrane; often contain one at least one transmembrane domain

• protein domain which passes through the cell membrane; mostly made of hydrophobic amino acids
• can only relay messages originating outside of the cell to the interior of the cell
• ​bind polar proteins
  
  • charged or have a lot of polar functional groups

Nuclear receptors- found in cytoplasm or nucleus

• bind to nonpolar, lipid-based ligands
  
  • steroid or thyroid hormones
  • can diffuse directly through membrane
• Once ligand binds, ligand-bound receptor migrates to the nucleus if its not already there
  
  • function as transcription factors, regulate rate of transcription

Question 388

Types of membrane receptors (3)

Answer 388

1. Ion channel linked (aka ligand gated)
   
   1. 2. Enzyme channel linked
   2. ​​
2. G-protein coupled receptors

Question 389

Ion channel-linked (aka ligand gated)

Answer 389

• contain transmembrane pores that allow ions to pass through when channel is open
• for channel to open, receptor must be bound by ligand
  • found on neurons, ligand is usually a neurotransmitter such as acetylcholine
  • if cell becomes more positive as a result, moves closer to electrical threshold, more likely to fire action potential
    
    • “depolarizes” neurons (aka excited)
    • efflux of negative ions from cytoplasm also depolarizes neurons
  • If movement of ions makes neuron more negative (like chloride ions), its moved further away from firing potential
    
    • inhibited, hyperpolarized

Question 390

Enzyme linked (catalytic) receptors

Answer 390

Either enzymes themselves or directly associated with enzymes they activate

• most commonly these enzymes are protein kinases, which phosphorylate (add a high energy phosphate group)
• Receptor Tyrosine Kinase (RTKs)
  
  • surface receptors for a bunch of hormones and growth factors
  • play a key role in cell growth when functioning properly
    
    • when not functioning properly, can contribute to a number of diseases (cancer)

Question 391

G-coupled receptor (GPCR)

Answer 391

• protein located in the cell membrane that binds extracellular substances and transmits signals from these substances to an intracellular molecule called a G protein (guanine nucleotide-binding protein).

Question 392

Gases

Answer 392

Play key roles in many biological processes: O₂, CO₂, Nitric oxide (cell signaling molecule)

Expandable and compressible, can change volume (unlike solids and liquids

Kinetic Molecular Theory, Ideal Gases

Question 393

Kinetic Molecular Theory

Answer 393

Gas can be understood as a system of tiny particles bouncing around inside a given region of space

• pressure on the walls of container is a result of elastic collisions of the particles with those walls
• Average kinetic energy is proportional to the temperature of the gas
  
  • U = 3/2kT
    
    • U = avg kinetic energy (1/2mv²)
    • k = a constant

​​​Brownian motion= couldn’t see gas particles but could see random jittery movement of pollen grains under light microscope, caused by movement of gas molecules

Question 394

Ideal Gases

Answer 394

Simplified manageable model of how gases behave:

• **Core assumptions:
  
  • Gas particles have no volume
  • Gas particles experience no attractive or repulsive forces

**Higher temp, high volume, and low pressure makes gases behave more ideally

• Minor assumptions:
  
  • collisions are perfectly elastic
  • motion is random

Question 395

Temperature conversions

Question 396

Boyle’s Law

Answer 396

Pressure and volume of a gas are inversely related

• P₁V₁ = P₂V₂
• or PV = constant (classic inverse relationship)

Question 397

Charles’ Law

Answer 397

Volume and temperature of a gas are directly related

Increased temperature expands its volume

ex. take air out of your tires in heat

• V₁/T₁ = V₂/T₂
• • V₁/T₁ = k (constant) (classic direct relationship)

Question 398

Avogadro’s Law

Answer 398

Volume of a gas is directly related to the number of moles of gas particles

• V₁/n₁ = V₂/n₂

Any two containers of gas with same volume will have same number of moles with same temperature and pressure, despite atom size (ideal gas law)

**Molar volume: 1 mole = 22.4 L at 273 Kelvin and 1 atm

(STP = standard temperature and pressure)

Question 399

Ideal gas law

Answer 399

PV = nRT

• R = ideal gas constant = .08206 L atm/mol K (use .08)
• or
• 8.314 J/ mol K
• ** values will be given on MCAT

Question 400

Real Gases equation

Answer 400

Gas particles do have a size and may be intermolecular forces between them

• Van der Waals euqation: modified ideal gas law
  
  • • (P + a/V²_m)(V_m - b) = RT
• • Volume - b is taking account for gas particle size
• Pressure is modified by “a”, a constant for each gas and V_m its molar volume

** Really polar molecule has larger “a” term, behaves more non-ideally; larger gas particles behave less ideally

Question 401

At large volume, is ideal gas pressure or real gas pressure higher?

At smaller volumes with higher molar concentrations of gas, is ideal pressure or real gas pressure higher? (under extreme conditions)

Answer 401

Ideal gas because real particle size still negligible but attractive forces bring particles together

Real gas pressure is higher

Question 402

Daltons Law of partial pressures

Answer 402

P_total = P₁ + P₂ + P₃…

Pressure that a gas exerts is independent of other gases present, depends on total pressure and mole fraction of gas

Mole fraction (X_n) = n_gas/n_total = P_gas/P_total

***P_gas = (X_gas)(P_total) - to get partial pressures

Question 403

Mole fraction

Answer 403

(X_n) = n_gas/n_total

Question 404

Graham’s law of effusion

Answer 404

When a gas is effusing (escaping from a small opening), smaller lighter particles escape faster

Rate 1/ Rate 2 = √((molar mass 2)/(molar mass 1))

Question 405

Respiratory sytem flow/anatomy

Answer 405

1. Air enters oral cavity (nostrils/nares)
   
   1. nasal cavity behind nostrils has a mucus membrane with tiny hairs called vibrissae that help filter particulate matter for first line immune defense (sneezing)
2. Air passes the pharynx at the back of the mouth and path diverges into the trachea and esophagus
   
   1. epiglottis is a flap of cartilaginous tissue, covers and protects trachea when swallowing, shunting food toward esophagus
   2. opens to allow air to flow into trachea during breathing
3. Air then passes the larynx, which contains the vocal cords
   
   1. vocal cords vibrate when air moves over them, consciously controlled during speaking/singing
4. Air continues down trachea, lined with ciliated epithelial cells and mucous producing goblet cells
   
   1. ​mucous traps stray bacteria/particulate matter, thrust upward by cilia to be expelled/swalled as phlegm
5. Trachea splits into two main bronchi, which themselves split off into bronchiole
   
   1. ​if bronchi become infected = bronchitis
   2. if bronchioles become infected = bronchiolitis
6. Smallest bronchioles terminate in air sacs known as alveoli
   
   1. ​where gas exchange occurs between alveoli and their capillaries
   2. 500 million alveoli for surface area
   3. alveoli very delicate, covered with surfactant, breaks up and reduces surface tension

Question 406

Epithelial cells

Endothelial cells

Goblet cells

Question 407

Alveoli

Answer 407

• Smallest bronchioles terminate in air sacs known as alveoli
  
  • ​where gas exchange occurs between alveoli and their capillaries
  • 500 million alveoli for surface area
• alveoli very delicate, covered with surfactant, breaks up and reduces surface tension

If alveoli become infected = pneumonia

Lungs are one of last forming organs in developing fetus, so premature birth gives risk to neonatal respiratory distress system – lungs collapsing due to insufficient surfactant production

• readily treatable by administering surfactant artificially until lungs are developed

Question 408

Gas Exchange in Respiration

Answer 408

Specialized alveoli

• alveolar wall is one cell thick, oxygen from air entering lungs diffuses readily across the membrane into alveolar capillaries
• blood in alveolar capillaries just returned from systemic circulation (CO₂ rich, oxygen poor)
  
  • oxygen diffuses from alveoli down concentration gradient, CO₂ follows concentration gradient into the alveoli
    
    • epelled from body during exhalation
• Oxygen entering blood quickly latches onto hemoglobin, oxygen carrier

Question 409

Lungs

Answer 409

Delicate, which is why they’re enclosed by a ribcage

• within thoracic cavity, lungs encased in two serous membranes
  
  • ​parietal pleura- lines the thoracic wall
  • pulmonary pleura- adheres to the lung
  • space between them is the pleural cavity
• during inhalation, muscular diaphragm beneath the lungs contracts, thoracic cavity expands –> reduced pressure in the pleural cavity causing lungs to expand
  
  • pressure and volume relationship

Question 410

Negative pressure breathing

Answer 410

Gases equalize pressures between regions of space; since volume and pressure have inverse relationship, increased lung volume reduces alveolar pressure

• causes air to flood the lungs to maintain equilibrium with ambient air
• lung air pressure becomes “negative” relative to ambient, forcing air to follow its pressure gradient

P₁V₁=P₂V₂

Question 411

Breathing

Answer 411

Can be voluntary or involuntary

• involuntary controlled by medulla oblongata of the brain system

Inhalation always an active process; downward contraction of the diaphragm requires energy

Exhalation is typically passive, but can be active

• abdominal muscles and internal intercostal muscles can produce more forceful
  
  • such as during exercise

Question 412

Respiratory volumes

Answer 412

Lungs capable of adapting to situations where oxygen needs are increased

Tidal volume- normal breathing

Inspiratory reserve volume- any additional air we could inhale

Expiratory reserve volume- any additional air we could exhale

Total lung capacity- total volume our lungs can hold

Vital capacity- maximum volume of air we could exhale

Residual volume- air remaining in lungs that can’t be exhaled (remains in alveoli so lungs don’t collapse completely)

Question 413

Use of respiratory volume metrics

Answer 413

Evaluating patients with pulmonary diseases like emphysema, COPD

Question 414

Respiratory immune defense

Answer 414

• Hair follicles in nose, cilia lined epithelial cells trap particulate and microbes
  
  • expelled by sneezing or cilia pushing mucous upward then coughing or swallowing

Respiratory tract also produces antimicrobial proteins called defensins, fight against bacteria, fungi and viruses

Loss of cilia from extensive exposure to cigarette smoke, increasing risk of infection

Question 415

Respiratory contribution to thermoregulation

Answer 415

Vessels in nasal cavity and trachea dilate in hot conditions to increase surface area through which heat can be radiated and lost to the environment

Constrict in cold conditions to retain heat as blood passes through

• These capillary beds can be sensitive; injury or dry conditions that cause mucous membranes to crack can cause nose bleeds
• Rely more heavily on other thermoregulation mechanisms, like sweating
• Furrier mammals can’t sweat to same extent, rely on panting/rapid breathing to lose heat via evaporative cooling

Question 416

Bicarbonate Buffer for circulation

Answer 416

• Carbon dioxide participates in equilibrium with carbonic acid and bicarbonate ions
• Largely travels through the bloodstream in the form of bicarbonate

In equation, elevated CO₂ directly translates to increased H+ concentrations, which acidifies the blood –> buffer system that helps maintains blood pH at ~7.4

• pH lower than this would be acidemia, higher pH would be alkalemia

Question 417

Peripheral chemoreceptor pathway

Answer 417

Chemoreceptors in the peripheral and central nervous systems detect oxygen, CO₂, and H+ concentrations in the blood

• why we feel urge to breath when we hold our breath, depleting oxygen and allowing CO₂ and H+ to build
  
  • in response, our respiratory rate speeds up to accelerate removal of CO₂ and replenish O₂ and return blood pH to normal
    *

Question 418

Blood circulates:

Answer 418

Oxygen

Nutrients

Essential ions

Proteins

Fluids

Metabolic wastes

Question 419

If you put blood in a centrifuge, it separates into:

Answer 419

1. Plasma- fluid component of blood
   
   1. 55% volume
2. Buffy coat- contains white blood cells and platelets (appears white)
   
   1. 1% volume
3. Erythrocytes (red blood cells)- carry gases, specifically oxygen and carbon dioxide
   
   1. usually around 45% = hematocrit

Question 420

Plasma

Answer 420

• fluid component of blood
  
  • about 55% of blood volume; carries ions, proteins, nutrients and gases
  • exercise can increase plasma volume to help circulate gases more readily

Question 421

Buffy coat

Answer 421

• contains white blood cells and platelets (appears white)
  
  • 1% of total volume
  • leukocytes: white blood cells, immune cells
  • • platelets: cell fragments from specialized cells called megakaryocytes
      
      • ​no nucleus
      • essential to coagulation (blood clotting);

Question 422

Coagulation Cascade

Answer 422

Clotting factors lead to a molecule called prothrombin being converted into thrombin

• thrombin converts fibrinogen into fibrin, a fibrous molecule that forms skeleton of a blood clot
• platelets then pile on top to form a platelet plug

Clot disintegrates as the wound heals – can sometimes not disintegrate and get lodged somewhere else

Question 423

Thrombosis and Thromboembolism

Answer 423

Blood clot doesn’t disintegrate and gets lodged somewhere else

• if occurs in the heart, can lead to heart attack
• in the brain, can result in a stroke

Question 424

Hemophilia

Answer 424

Missing one of the factors required to form blood clots, more susceptible to excessive bleeding

Question 425

Erythrocytes

Answer 425

Red blood cells, carry CO₂ and oxygen in the blood by carrying millions of copies of hemoglobin molecules

Produced in red bone marrow of flat and long bones, just like white blood cells

• body releases a horomone called erythropoietin (EPO) from the kidneys to stimulate production
  
  • (can inject in yourself for blood doping)
• 45% of volume of blood
  
  • hematocrit- proportion of your blood that is composed by red blood cells

Just as they are about to mature to adult red blood cells, erythrocyte cells eject their nucleus and other organelles

• makes them extremely energy efficient, but can’t live very long (~120 days)
  
  • sent to the spleen for destruction

Question 426

Spleen function

Answer 426

it fights invading germs in the blood (the spleen contains infection-fighting white blood cells) it controls the level of blood cells (white blood cells, red blood cells and platelets) it filters the blood and removes any old or damaged red blood cells.

Question 427

Erythrocytes (red blood cells) coat themselves with

Answer 427

Glycoproteins (sugar-coated proteins) on cell surface

ABO blood typing is based off which ABO glycoproteins are expressed on a person’s red blood cells

• depends on persons genotype
  
  • A antigen = blood type A
  • B antigen = blood type B
    
    • both = AB
  • neither = blood type O

Question 428

Blood type alleles

Answer 428

AB = codominance, both alleles expressed

Question 429

Blood type is important because

Answer 429

Immune system produces antibodies against ABO blood types we don’t produce

• A blood type produces anti-B antibodies
• O blood type produces anti-A and anti-B antibodies

Question 430

O blood type

Answer 430

Universal donor; doesn’t contain any ABO antigens

People with O type can only receive O type

Question 431

Rh factor

Answer 431

Antigen that can be expressed on red blood cells

• either Rh+ or Rh-

A+ means you have A antigen and Rh factor antigen

If an expecting mother is Rh- and her fetus is Rh+, her immune system makes anti-Rh antibodies that may attack her fetus

• mother is given anti-Rh antibodies preventing her immune system from needing to make its own

Question 433

Two parts of circulatory system

Heart pumps ~2000 gallons of blood a day

Answer 433

1. Systemic- takes oxygen rich blood to bodys tissues then returns oxygen depleted blood back to heart
2. Pulmonary- circulatory system through the lungs

Question 434

Pulmonary circulation

Answer 434

Blood flows through vessels adjacent to alveoli (air sacs) of the lungs; oyxgen from the lungs flows across into the blood vessels while CO₂ flows into the lungs to be exhaled

• oxygenated blood returns to the heart, which is pumped back into systemic circulation

Question 435

3 types of blood vessels

Answer 435

Arteries, capillaries, veins

Question 436

Arteries

Answer 436

Carry blood away from the heart

• Not always oxygenated, pulmonary artery carries deoxygenated blood from heart to lungs
• Umbilical arteries carry deoxygenated blood from fetus to placenta; becomes oxygenated and back to fetus

Thick muscular walls

Adaptable; vasoconstriction to certain parts of body and vasodilation to others when needed(like fight or flight)

Aorta: body’s largest artery, from left ventricle to rest of body

Question 437

Arterioles

Answer 437

Arteries branch off into smaller arteries called arterioles; this is where blood pressure begins to lower

Arterioles lead to capillaries

Question 438

Capillaries

Answer 438

Branch off from arterioles; very small and thin - walls are one cell thick of endothelial cells

• red blood cells file through them one by one
• creates ideal environment for gas exchange to occur across thin capillary walls
  
  • oxygen flows into tissues and CO₂/urea into the blood

Very small but so many of them that cross sectional area is greater than any other point in circulatory system = slowest blood velocity

Delicate; blood spilling out causes bruising

Question 439

Veins

Answer 439

Carry blood towards the heart

• branch off as venules from capillary beds and merge into veins which connect directly to the heart

Thinner, less muscular walls than arteries do; blood pressure is lower than arteries

• working against gravity – require one way valves towards heart preventing backflow
• also rely on skeletal muscles to squeeze veins

Question 440

Arteries and veins have 3 layers:

Answer 440

1. Tunica externa- outermost layer
2. Tunica media- middle layer of smooth muscle
3. Tunica intima- innermost layer, endothelial cells

Question 441

1 cause of death in the United States

Answer 441

Cardiovascular disease

Question 442

Pathogenesis

Answer 442

Manner of development of a disease

Question 443

Atherosclerosis

Answer 443

Fatty plaques can build up in arteries, making it more diffficult for blood to reach body tissues

In the heart, can lead to heart attack

Question 444

Heart’s chambers

Answer 444

Right and left atria- two chambers on the top

Right and left ventricles- two chambers on the bottom

Question 445

Atria chambers

Answer 445

Collecting chambers; blood enters from systemic and pulmonary systems

• Funnel blood into the ventricles
• Right atrium- deoxygenated blood from systemic circulation
• Left atrium- receives oxygenated blood from pulmonary veins
  
  • funnels blood into left ventricle

Question 446

Ventricle chambers

Answer 446

Blood funneled in from atria; thick, muscular walls that contract to eject blood out of the heart

Right ventricle- pumps deoxygenated blood through pulmonary artery into the lungs

• blood gets oxygenated, pumped through pulmonary veins back into left atrium of heart

Left ventricle- pumps blood through the aorta, body’s largest artery, to the rest of the body

Question 447

Inferior and superior vena cavae

Answer 447

Return deoxygenated blood to the right atrium

Question 448

Atrioventricular valves

Answer 448

Control blood flow between atria and ventricles

• Triscupsid valve (right side)
• Bicuspid valve (mitral)(left side)

Question 449

Aortic and Pulmonary valves

Answer 449

Between ventricles and their respected arteries

Question 450

Systole

Diastole

Answer 450

When ventricles contract (blood pressure skyrockets)(peak)

Heart relaxes (blood pressure drops back down)(lower)

Question 451

blood pressure

Answer 451

Systole / diastole

• healthy is usually under 120/80 mmHg

Question 452

In a capillary bed, plasma is often…

Answer 452

Forced into spaces between cells and picked up by lymphatic capillary to return to circulation

Question 453

Heart and nervous system

Sympathetic and parasympathetic effect

Hormones and heart rate

Answer 453

Heart receives signals from nervous system to slow down/speed up but heart can beat on its own due to its own electrical system

• Without nervous system, heart would be oblivious to environmental and chemical cues
  
  • Sympathetic (fight or flight): can speed up heart rate
  • Parasympathetic (rest/digest): can slow down the heart rate

Heart rate can also be increased by hormones epinephrine and norepinephrine from adrenal medulla

Question 454

Heart’s electrical system

Answer 454

Starts wtih Sinoatrial (SA) node- instructs atria to contract and send blood to ventricles

• signal travels from SA node to AV node

​Atrioventricular node (AV)- sits at junction between AV and ventricles, helping transmit signal to ventricles

• signal transmitted to Bundle of His and Purkinje fibers
• ventricles contract to push blood out and into sytemic and pulmonary circulation

Question 455

Gap junctions

Allow flow of?

Located in?

Answer 455

Membrane ion channels, allow ions to flow between individual muscle cells

• all fibers depolarize and contract at the same time

Located in intercalated discs: structures that connect neighboring cardiac muscle cells

Question 456

Sinoatrial node (SA)

Answer 456

Heartbeat starts; in the right atrium where a group of pacemaker cells live

• Pacemaker cells fire off electrical signals that instruct the heart to contract 60-100 times/min
• send action potentials to the atria, causing it to contract & push blood into ventricles
  
  • cardiac muscle fibers in atria contract simultaneously due to gap junctions

Question 457

What does muscle contraction require

Answer 457

ATP –> mitochondria –> oxygen –> lungs

Question 458

Hemoglobin function

Answer 458

Extracts air from the lungs, carries it through the blood, releases it in vicinity of bodies tissues

Oxygen binding molecule inside red blood cells (erythrocytes)

• gives red blood cells and blood cells the red hue
• Metalloprotein with 4 subunits: two alpha and two beta
  
  • each subunit has a heme group: heterocyclic porphryn ring with iron 2+ ion in the center *****binds oxygen
    
    • can bind 4 oxygen molecules

**Also binds CO₂ on the way back to the lungs for expiration

Any red blood cell contains hundreds of millions of hemoglobin

Question 459

Oxygen binding to hemoglobin is…

Answer 459

Cooperative: number of oxygen molecules bound to a hemoglobin molecule at any given time affects how likely it is to bind more oxygen molecules – changes conformation

• In high oxygen environments, once hemoglobin binds one it is more likely to bind more
  
  • • In low oxygen environments, the removal of one oxygen makes it more likely for a second, third, fourth to dissociate

Question 460

Cooperative binding

Answer 460

Binding of a ligand at one site of a molecule influences binding at another site

Question 461

Hemoglobin conformations

Answer 461

T (taut) state: low oxygen conditions, low affinity for oxygen

R (relaxed) state: when oxygen binds, switches to have high affinity for oxygen

• results in oxygen binding by hemoglobin being favored when large amounts present like in lungs
• disassociation when low amounts like in tissues

Question 462

Hemoglobin Oxygen Dissociation Curve

Answer 462

Sigmoidal shape due to cooperative binding

• low oxygen concentrations (like exercising tissues), oxygen dissociates from hemoglobin & adopts T state
  
  • • at higher concentrations, loads up on as much oxygen as possible –> R state

Curve affected by chemical environment:

• exercise causes production of CO₂ and lactic acid, making blood more acidic
  
  • also generating a lot of heat
  • causes curve to shift to down and to the right
    
    • _​_oxygen bonded less well, more free to dissociate into tissues
  • high 2,3-BPG = byproduct of glycolysis
• • curve for fetal hemoglobin shifted left, higher affinity and can steal hemoglobin from maternal circulation

Question 463

Sickle cell anemia

Sickle cell trait

Answer 463

If just one specific amino acid in hemoglobin protein is mutated from glutamate to valine –> hemoglobin aggregates in low oxygen environment

• causes red blood cells to adopt a sickle shape
  
  • Misshapen red blood cells can clog capillaries and become destroyed more easily - life threatening condition

Those with one copy of mutation instead of two have sickle cell trait, milder form of disease which can confer protection against malaria

Question 464

Myoglobin

Answer 464

Oxygen storing in muscle

• only one subunit
• no cooperative binding

Higher affinity for oxygen than hemoglobin – steals oxygen from hemoglobin

Iron in myoglobin gives meat it red hue

Question 465

Enteric nervous system

Answer 465

Nervous system dedicated entirely to function of digestive system

Question 466

Salivary amylase

Lingual lipase

Lysozyme

Answer 466

Salivary anylase breaks down starch into smaller oligosaccharides and disaccharides (why starchy foods taste sweet if on your tongue long enough)

Lingual lipase begins process of digesting lipids (fats)

Lysozyme is an antimicrobial enzyme strong enough to kill off some bacteria

Question 467

Gastrointestinal tract - following food from mouth to stomach

Answer 467

Highly specialized to extract nutrients - receives help from gut bacteria and enteric nervous system

Three major biomolecules - carbohydrates, proteins, lipids

1. Before food hits tongue, salivary glands produce enzyme rich saliva (also lubricates food)
   
   1. enzymes digest carbohydrates and lipids (not proteins), antimicrobial
2. Bolus (food) proceeds down esophagus by peristalsis
3. Bolus is emptied into the stomach, passing through the lower esophageal sphincter (cardiac sphincter)
   
   1. bolus is digested into chyme: acidic mixture of semi-digested food and gastric juices
   2. chyme passes through pyloric sphinctor into the small intestine

Question 468

Esophagus

Answer 468

Fibromuscular tube through which food passes to the stomach

• runs behind trachea and pierces through diaphragm en route to the stomach

Moves bolus downward by wave-like contractions of the smooth muscle lining, known as peristalsis

• can eat if upside down

Question 469

Epiglottis

Answer 469

Flap of cartiledge that covers the trachea during swallowing to prevent food from traveling down the wrong pipe

Question 470

Lower esophageal sphincter (cardiac sphincter)

Answer 470

Gate through which food can pass from eosphagus to stomach, but blocks contents of stomach from passing back up into the esophagus

except for Gastroesophageal Reflux Disease (GERD): caused by acidic contents of stomach escaping into esophagus when lower sphincter is weakened

Question 471

Stomach

pH?

Secretions?

What can the stomach absorb?

Answer 471

Highly acidic chamber (great for breaking down macromolecules)

Parietal cells of the stomach secrete gastric acid: composed of hydrochloric acid and various salts

• keeps stomach pH between 1.5 and 3.5

Chief cells secrete inactive pepsin-precursor (zymogen) called pepsinogen, cleaved in acidic conditions to enzyme pepsin, which does most of protein digestion

Stomach also produces intrinsic factor: necessary to absorb vitamin B12; and water to dilute the bolus

Stomach can absorb water and certain drugs like aspirin, caffeine, small amounts of alcohol

Question 472

Zymogen

Answer 472

Inactive precursor to enzymes

Question 473

Benefits of acid in stomach

Answer 473

Helps with biomolecules digestion (HCl activates pepsinogen)

Neutralizes bacteria (not H. pylori)

Question 474

How does stomach protect itself from acidic conditions?

Answer 474

Mucous epithelial cells produce bicarbonate rich mucous that neutralizes gastric acid at the lining of the stomach, providing protection

Question 475

H. pylori

Answer 475

Bacteria in ~half of the world’s stomachs which fluorish in it’s acidic environment

• most people never experience symptoms but in some, bacteria can erode the lining of the stomach and cause painful peptic ulcers

Pylori comes from being located in the bottom of the stomach (the pylorus)

Question 476

Gastrointestinal tract- stomach to large intestine

Answer 476

1. Chyme exits stomach through pyloric sphinctor into the small intestine
   
   1. food contents move through small intestine by peristalsis- waves of smooth muscle contraction just like in esophagus
2. Once food reaches duodenum, triggers release of hormones that promote digestion
   
   1. secretin: stimulates secretion of bicarbonate which quickly neutralizes acidic chyme (pH 6-7)
   2. CCK: stimulates release of digestive enzymes from pancreas and bile from gallbladder
3. Receives response in form of digestive enzymes from pancreas and bile from the gallbladder
   
   1. brush border enzymes also aid
4. Once carbohydrates, lipids, proteins all digested into smallest units: monosaccharides, fatty acids, and amino acids absorbed by epithelial lining cells
   
   1. Enter the circulatory system (fats take different route there by lymphatic system)
5. Any remaining undigested material passes to large intestine where it is converted to feces
   
   1. ​Feces primarily contain water and indigestible material (cellulose from plants; humans lack enzymes to digest)
      
      1. reason celery is low calory, can’t derive energy

Question 477

Small intestine brush border

Answer 477

Moves food through it via peristalsis

• invaginates in a series of folds that are composed of microscopic villi that project into the lumen

Enterocytes: intestinal epithelial cells that line the intestines

• each enterocyte has hundreds of finger-like extensions of plasma membrane called microvilli
  
  • Greatly increase absorptive surface area (6 ft² –>2700 ft²)
• secrete brush border enzymes: disaccharidases and peptidases

Question 478

Small intestine is partitioned into

Answer 478

1. Duodenum
2. Jejunum (longer)
3. Ileum

Dow Jones Industrial

Question 479

Gallbladder

Answer 479

Gallstones- accumulate in painful fashion in gallbladder

Located just below the liver, gallbladder is small sac that stores bile produced in the liver

Question 480

Bile

Answer 480

Yellow-green fluid produced in the liver that contains bile salts which facilitate fat absorption

Amphipathic- contain polar and nonpolar regions; nonpolar regions associate with triglycerides and polar regions associate with water on outside

• Forms spherical micelles that emulsify lipids in an aqueous environment
  
  • lipid emulsification: breaks up lipids, exposing surface area to water soluble lipase enzymes
  • also facilitates absorption by enterocytes in small intestine

Bile salts themselves aren’t enzymes

Question 481

Liver functions (5)

Answer 481

• capillaries of small intestine drain into the hepatic portal vein which enters hepatic portal system of liver
  
  • pick up nutrients and drugs from digestive organs and are sent to second capillary system in liver for processing

1. Secretes bile
2. Detoxifies compounds
3. Metabolizes drugs and medications
4. Stores glycogen and triglycerides
5. Mobilizes glucose and fatty acids

Question 482

Portal system

Answer 482

System of blood vessels with capillary bed at each end

• ex. hepatic portal system for liver, hypophyseal portal system in hypothalamus

Question 483

Pancreas

Answer 483

In response to hormonal signals from small intestine, pancreas secretes an alkaline fluid containing digestive enzymes into pancreatic duct: drains into duodenum

• Enzymes include:
  
  • pancreatic amylase: digests sugars into disaccharides
  • pancreatic lipase: digests triglycerides into fatty acids and monoglycerides
  • various proteases that digest proteins into amino acids and small peptides
• enzymes work best at alkaline pH

Question 484

Pancreas dual function

Answer 484

Pancreas has exocrine and endocrine function

• Exocrine: secretes enzymes through pancreatic duct
  
  • • Endocrine: releases hormones into bloodstream

Question 485

Large intestine subdivisions

Answer 485

• Cecum: pouch connected to ileum of small intestine via iliocecal sphincter
  
  • ​appendix: atttached to cecum; vestigial organ (serves no purpose)(may be a reservoir for healthy gut bacteria)
• Colon: longest segment that goes over small intestine
  
  • 1. ascending colon
  • 2. transverse colon
  • 3. descending colon
  • 4. sigmoid colon
• Rectum
  
  • ​stores feces prior to excretion past anal sphinctor and to the anus

Question 486

Large intestine main function

Answer 486

Absorb water from chyme converting it into solid feces

• Nutrient absorption is limited
• Gut flora/microbiota: hosts the largest community of bacteria in human body
  
  • synthesize necessary vitamins B7 (biotin) and K (blood coagulation) which are absorbed

Laxatives interfere with water absorption in large intestine without affecting nutrient absorption in small intestine

• ease constipation but not good for weight loss

Question 487

Feces pathology

Answer 487

Liver dysfunction: affect bile production and lipid digestion, more fat excreted in feces = steatorrhea

Question 488

Endocrine hormones that regulate digestion affect…

Answer 488

Affect appetite

Stimulate digestion

Halts digestion

Question 489

Endocrine appetite hormones

Answer 489

• leptin- hormone secreted by fat cells (adipocytes) that helps suppress appetite (feelings of fullness)
  
  • failed to live up to hype in pharmaceutical world
• ghrelin- secreted by specialized cells in pancreas and upper stomach when stomach is empty; increases appetite
  
  • hunger hormone, “grrrrelin”
  • • gastric bypass surgery removes many of these upper stomach cells

CCK can also inhibit appetite

Question 490

Endocrine digestion stimulation hormones

Answer 490

Digestion stimulated by signals indicated food has been ingested

• in stomach, G cells secrete gastrin: tells parietal cells when to produce HCl and intrinsic factor (gastric acid)

When acidic chyme reaches duodenom of small intestine, S cells release secretin: stimulates release of bicarbonate to neutralize chyme

Cholecystokinin also released from small intestine stimulates excretion of digestive enzymes from pancreas and bile from gallbladder

• inhibits appetite

Question 491

Endocrine hormones that halt digestion

Answer 491

• Somatostatin: halts pro-digestion hormones- gastrin, secretin, CCK
  
  • also stalls stomach emptying and halts release of pancreatic insulin and glucagon
    
    • also inhibits growth hormone release

Empty stomach promotes appetite, inhibits digestion

Full stomach inhibits appetite and stimulates digestion

• stomach acid and pancreatic secretion are stimulated

Question 492

Enteric Nervous System “Second Brain”

Answer 492

Considered a branch of autonomic nervous system, not under conscious control

• other branches of autonomic also have implications on digestive tract
  
  • sympathetic “fight or flight” contracts blood vessels to GI to direct them to muscles
  • parasympathetic dilate blood vessels to GI tract to promote digestive system

Question 493

Why does your body need to digest lipids

Amino acids

Carbohydrates

Answer 493

Maintain cellular membranes, energy storage

Synthesize new proteins

Primary source of energy

Question 494

Sequential digestion of carbohydrates

Answer 494

1. Salivary amylase breaks starches into trisaccharides and disaccharides
   
   1. 2. Stomach doesn’t enzymatically digest carbs but does so mechanically, increasing surface area exposed to enzymes in small intestine
   2. 3. Cholecystokinin induces pancreatic digestive hormones when chyme enters duodenum
   3. Pancreatic amylase hydrolyzes polysaccharides into di- and tri-
2. Brush border disaccharidases secreted by enterocytes in small intestine turn disaccharides into monosaccharides
   
   1. sucrase: sucrose into glucose and fructose
   2. maltase: maltose into two glucose
   3. lactase: lactose into glucose and galactose
      
      1. individuals deficient for lactase can’t digest lactose from milk/dairy
      2. indigested lactose passes to large intestine and fermented by bacteria –> results in gas (bloating, discomfort, flatulence)

Question 495

Lactose intolerance in the world

Answer 495

Most of the world adults stop expressing lactase, incapable of digesting lactose

• Lactose tolerance thought to have evolved due to mutation thousands of years ago, strong selective advantage
• Mostly european ancestry

Question 496

Uptake of glucose after breakdown

Answer 496

Intestinal epithelial cells take up monosaccharides like glucose for passage into bloodstream (Glucose= 80% of monosaccharides)

Sodium-potassium pump uses ATP to pump 3 sodium out of cell into bloodstream, 2 potassium into cell

• creates electrochemical gradient, sodium can passivly flow back into cell from _intestinal lumen v_ia sodium-glucose symporter
  
  • lets one glucose tag along for every 2 Na into cell
• Glucose then travels via facilitated diffusion through a glucose uniporter out of cell into circulatory system

Secondary active transport: Na+ glucose symporter relies on active transport from sodium potassium pump to create concentration gradient

Question 497

Uptake of galactose and fructose into bloodstream

Cellulose and other undigested starches

Answer 497

Galactose has similar method to glucose absorption (secondary active transport)

Fructose by facilitated diffusion

Cellulose and other undigested starches travel to large intestine and metabolized by gut flora

Question 498

Digestion of proteins

Answer 498

Isn’t digested until the stomach, where stomach acid cleaves pepsinogen into enzymatically active form pepsin, which hydrolyzes peptide bonds in proteins

• **targets sites between hydrophobic or aromatic amino acids
  
  • doesn’t completely break down to amino acid level

Pancreatic enzymes induced by cholecystokinin hormone triggered by acidic chyme in duodenum (small intestine)

• trypsinogen cleaved by enteropeptidase into active form, trypsin
  
  • ​trypsin: cleaves peptide bonds adjacent to lysine and arginine residue which activates suite of proteases
• • ** Enzymatic regulation avoids premature activation of proteases
    
    • if prematurely activated, digest/damage the pancrease = pancreatitis

Question 499

Zymogen

Answer 499

Inactive precursor molecule

Question 500

Uptake of amino acids after breakdown

Answer 500

Like glucose, aminos absorbed by intestinal lumen cells via secondary active transport

• cotransport with sodium ions following concentration gradient established by Na-K pump
  
  • exits cell via facilitated diffusion into bloodstream

Question 501

Why is uptake of amino acids and sugars similar

Answer 501

Both use secondary active transport with sodium potassium pump

**Monomeric sugars and aminos more or less hydrophilic, readily dissolve in aqueous environment of intestinal lumen

• lipids are hydrophobic, not readily dissolvable

Question 502

Lipid absorption in small intestine

Answer 502

Dietary lipids are triglycerides, must be processed into fatty acid and monoglyceride components by lipase enzymes

• occurs to minimal extent in oral cavity by lingual lipase, more so in small intestine by pancreatic lipase

Spherical micelles created by amphipathic bile salts easily diffuse through plasma membrane of intestinal epithelial cells due to hydrophobic components

• In cytoplasm, fatty acids reform with monoglycerides to form triglycerides which are packaged into chylomicrons
  
  • instead of diffuse into bloodstream, chylomicrons diffuse into lacteals:
    
    • ​small lymphatic vessels that drain into larger lyymphatic vessels before going in circulation

Question 503

Digestion efficiency

Answer 503

Extraction of macromolecules occurs hours after consumption

• 1.5L of saliva, 2 L of pancreatic solutions a day

Question 504

Vitamins

Answer 504

Organic molecules with lots of carbon-hydrogen bonds

Often serve as coenzymes for essential processes

• ex. vitamin K a coenzyme in blood clotting

Question 505

Fat soluble vitamins

Water soluble vitamins

Answer 505

Vitamin A, D, E, K

• accumulate in adipose (fat tissue)
• too much can result in consequences
  
  • excess vitamin A from carrots cause turn skin orange from buildup in subcutaneous(under skin) fat

Vitamins B, C (a couple B vitamins stored in liver)

• circulate in the blood and are easily excreted
• almost impossible to take too much

Question 506

Vitamin A

Answer 506

Retinal and retinol

• essential for vision
• interacts with opsin to form rhodopsin, which is present in the rods of the retina
  
  • Used for low light vision

Fat soluble

Question 507

Vitamin D

Answer 507

Acts as a hormone that regulates calcium and phosphate concentrations in the blood stream (increases absorption in small intestine)

• can be synthesized in the skin from exposure to UV radiation
• two major forms converted to active form calcitriol

Fat soluble

Question 508

Vitamin K

Answer 508

Synthesized by bacteria in the large intestine

Essential for blood coagulation

Fat soluble

Question 509

Deficiency in Vitamin C (ascorbic acid)

Answer 509

Common with sailors, no fresh food

• scurvy: weakness, gum disease, excess bleeding, death

Vitamin C required for collagen synthesis

Question 510

Minerals

Answer 510

Inorganic substances required but not synthesized by the body; must be obtained in diet

• like metal ions

Macrominerals: required in significant amounts; Calcium, sodium, potassium

Trace minerals: iron, zinc, copper

Cofactors in vital processes: calcium in muscle contraction, zinc in DNA and protein synthesis

Question 511

Thermodynamics definition

Heat vs. temperature

Answer 511

Study of heat

Temperature: measure of hotness proportional to kinetic energy

• high temp means on avg molecules are moving rapidly

Heat: transfer of energy between two objects with a temperature difference (trying to reach an equilibrium)

• when boiling water, imparting kinetic energy to its molecules and since temp is proportional its temp rises also
  
  • increases speed of water molecules until they overcome intermolecular interactions

Question 512

Kinetic energy of Ideal Gases equation

Answer 512

KE_particle = 1/2 m_particle v_rms²

• root mean square velocity = √ 3RT / M_m
  
  • R = Ideal gas constant
  • M_m = molar mass
  • T = temp (kelvin)

Temp and KE related

Question 513

Fahrenheit scale points of water

Answer 513

Freezing point of water: 32 deg

Boiling point: 212 deg

Question 514

Celsius scale

Answer 514

Freezing pt of water = 0 deg, boiling point = 100 deg

Body temp is 37 deg

Question 515

Converting between Celsius and Fahrenheit

Kelvin to Celsius

Answer 515

• C = (F - 32) x 5/9
• F = (C x 9/5) + 32
• K = C + 273.15
• • C = K - 273.15

Question 516

Kelvin

Answer 516

0 = absolute temperature: lowest possible temp where motion ceases

• celsius absolute temp = -273.15 C

*** most thermodynamic equations use Kelvin but may give you Celsius, must be able to convert

Question 517

Heat

Types of heat transfer (3)

Answer 517

Thermal energy transferred between two substances at different temperatures

• energy = Joules (kg x m²/ s²)
  1. Conduction
  2. Convection
  3. Radiation

Question 518

Conduction

Answer 518

Transfer of heat/kinetic energy via direct contact

• occurs across all phases of matter
  
  • metals are excellent conductors due to delocalized electrons
  • insulators don’t conduct heat well

Question 519

Convection

Answer 519

Conduction with movement; direct transfer of KE from one substance to another

• however, focuses on circulations of fluids (gas or liquid)

Air that is heated will expand and rise and be replaced by cooler contracting air; supply of heat constantly being replenished

Question 520

Radiation

Answer 520

Does not require direct contact between substances

Energy is transferred via electromagnetic waves

• **electromagnetic waves are produced by all objects and carry a certain amount of energy
  
  • sunlight, heat from a fire, light bulb, thermal energy from bodies

Question 521

Expansion due to heat

Answer 521

• When a substance heats up, molecular motion and separation increases
• substance generally expands, density decreases
  
  • ice is less dense due to unique configuration of crystal structure of ice
• • Linear expansion: solid or liquid expands in length
    
    • ∆L = a_LL∆T
    • a is coefficient of thermal expansion
• • Volume expansion:
    
    • ​∆V = a_vV∆T

Question 522

Work done on a gas expanding or compressing

Pressure equation

Answer 522

W = - P∆ V (J)

P = F / A

Question 523

Work is negative when

Work is positive when

Answer 523

It is being done by the system (gas) on the environment

• energy is being lost to environment

Being done on the system (gas) by the environment

• system is gaining energy

Question 524

Pressure volume graph

Answer 524

Question 525

Laws of Thermodynamics

Answer 525

0. Zeroth Law: If state A is in thermal equilibrium with states B and C, then states B and C must be in thermal equilibrium with each other

1. Law of conservation of energy: energy can neither be created or destroyed

• can be transformed or move with the system (universe, only truly isolated system)

2. ∆S_universe ≥ 0

• The entropy of a system will naturally increase over time

3. At absolute temperature (0 K) a pure crystal has no entropy

Question 526

1st law of thermodynamics

Answer 526

Conservation of energy: energy can neither be created nor destroyed, only transformed or moved

In Closed Systems:

∆U = Q - W

• change in internal energy = heat transfer into system - work performed by the system
  
  • if system performs work, loses energy to environment
  • positive value if work is done on the system

Doesn’t apply in open systems

Question 527

Entropy (S)

Answer 527

energy not available to do work

• greater number of possible molecular configurations, the greater the entropy
  
  • liquid has greater entropy than solid
• greater number of molecules generally means greater entropy

Change in entropy for a reversible process: ∆S = Q / T

Entropy can decrease but it requires energy

Question 528

2nd law of thermodynamics

Answer 528

2. ∆S_universe ≥ 0

• The entropy of a system will naturally increase over time
  
  • entropy (S) = energy not available to do work
• If two objects are in contact but not thermal equilibrium, heat energy will spontaneously go from higher to lower temp

Entropy can decrease but it requires input of energy, however entropy of surroundings increase more so entropy of universe increases

Question 529

Energy (U) is defined as

Answer 529

the ability to do work

Question 530

Calorimetry

Answer 530

Calorimetry mimics combustion, which is how our body processes nutritional calories

• molecules consumed in presence of oxygen, producing water and CO₂
• derives energy

Heat can be measured in Joules or Calories (not the nutritional calorie)

• 1 cal = 4.184 J

Question 531

Types of calorimeters

Answer 531

Calorimeter- measures heat energy produced by burning a substance

• by using change of temp of water
• Q = mc∆T
  
  • ​m = mass of water
  • c = specific heat capacity of water

Bomb calorimeter

Coffee cup calorimeter

Question 532

Heat can be measured in…

Answer 532

Joules

1 cal = 4.184 J

1 Cal = 1000 cal (1 kcal) = nutritional value

Question 533

A calorie is defined as

Answer 533

The amount of energy required to raise the temp of 1 gram of water by 1 deg C

Question 534

Specific heat capacity and equation

Answer 534

Specific heat capacity (c): energy required to raise heat of 1 gram of substance by 1 deg C

Q = mc∆T

c of water = 4.186 J/g x C or 1 cal/g x C

Question 535

Enthalpy (H)

equation

Answer 535

Enthalpy (H): total heat in a thermodynamic system in Joules

• ∆H = ∆U + P∆V

U =internal energy

P∆V = W –> ∆H = ∆U + W Q = ∆U + W –> ∆H = Q

• ∆H is equal to heat lost or gained in a system

Question 536

Endothermic process (enthalpy)

Exothermic process

Answer 536

Heat is added to a system, ∆H > 0

• much of the heat put into an endothermic rxn is used to break bonds and enable the chemical rxn

Heat is removed from a system, ∆H < 0

Question 537

Standard enthalpy (∆H°)

Standard enthalpy of formation (∆H_f)

Answer 537

∆H° = enthalpy change under standard conditions

standard conditions = 1 atm, 25 deg C

The enthalpy change associated with forming one mole of a compound from its elements under standard conditions

• element + element = compound (1 mole)
• standard enthalpy of any element in standard state is 0
  
  • ∆H_f of O₂ = 0

Question 538

Standard enthalpy of reaction

Answer 538

∆H° of rxn = Σ∆H° of products - Σ∆H° of reactants

Given enthalpy values of reactants/products in J/mol, must factor in the amount of each compound

Use rounding and estimation

Question 539

Bond dissociation energy (enthalpy)

Answer 539

Enthalpy change associated with breaking bonds

∆H°_reaction = ∆H°_{bonds broken (reactants)} - ∆H°_{bonds formed (products)}

Opposite of standard enthalpy of reaction

• Forming bonds = exothermic, more stable/less energy after
• breaking bonds = endothermic

Will be given values for single bonds, double bonds, etc

Question 540

Hess’s Law (total enthalpy)

Answer 540

∆H_rxn = ∆H₁ + ∆H₂ + ∆H_3…

Each step must be ordered in the proper direction; reverse the sign when reversing the order of a component step, and multiply by number of moles required

Question 541

Spontaneous reaction

Nonspontaneous reaction

Answer 541

Will proceed spontaneously on its own

Requires energy input

Thermodynamics vs. Kinetics: spontaneity unrelated to reaction rate

Question 542

Gibbs free energy (∆G)

Activation energy (E_a)

Answer 542

Energy that can be used to perform work in a reversible reaction

• only accounts for starting state of reactants and final of products
  
  • if free energy decreases and products are lower energy/more stable, reaction wants to occur
    
    • ∆G < 0 , reaction spontaneous = exergonic
    • ​
    • ∆G > 0 is nonspontaneous, endergonic

∆G_rxn = products - reactants

Question 543

What determines free energy state of a system (Gibbs free energy, G)

Answer 543

Enthalpy, entropy, and temperature

∆G = ∆H - T ∆S

T is in Kelvin ** almost always

Conditions for spontaneity (-∆G) : see picture

Question 544

Thermodynamics vs. Kinetics

Answer 544

Thermodynamics: Stability of products/reacts, spontaneity, and equilibrium

Kinetics: rate of reaction, activation energy, rxn mechanisms

Spontaneity UNRELATED to rate of reaction

Question 545

Equillibrium constant (equation)

Answer 545

Rate_forward = Rate_reverse at equilibrium

K_eq = [products]^x / [reactants]^y

• raised to coefficients in balanced equation

**tells us the tendency of rxn to progress one way or the other

• concentrations at equilibrium, changes at different temps

**If Keq > 1, products are favored over reactants and ∆G is negative = spontaenous in forward direction

**If Keq < 1, reactants favored and ∆G > 0, non spontaneous

**If Keq = 1, ∆G = 0 and reaction is in equilibrium

******can’t use gases or solids, no H₂O

∆G = -RT ln Keq

Question 546

∆G under non standard conditions (not 1 atm, 25 deg C, 1 mole)

Answer 546

∆G = ∆G° + RT ln Q

K_eq = [C]^c [D]^d / [A]^a [B]^b at equilibrium

Q = [C]^c [D]^d / [A]^a [B]^b at any point in rxn

• if Q > Keq, products higher than at equilibrium and goes in reverse
• when Q < Keq, reactants move in forward direction
• when Q = 0, equilibrium

Question 547

Catalysts

Answer 547

Needed when a reaction can’t surpass activation barrier on its own

• Enzymes
• increases rate by lowering activation energy in both directions

Question 548

Protein folding refers to…

Answer 548

Globular proteins

• • Spherical
    
    • myoglobin
    • • Serve functional roles
    • enzymes, peptide hormones, regulatory molecules
    • • Generally water soluble

Question 549

Types of proteins

Answer 549

Globular- spherical, water soluble, serve function, protein folding

Fibrous- elongated (sheet-like), hydrophobic, ex. collagen

Membrane proteins- attached to plasma membrane

Question 550

Why does protein folding occur (tertiary structure)

Answer 550

• Entropy- increase in entropy is favorable
  
  • Folded protein has lower entropy than unfolded, however, hydrophilic solvents lose entropy when they form solvation layer arond hydrophobic side chains
• • protein folding conceals hydrophobic side chains
• minimal contact with hydrophobic side chains = maximum entropy

** protein folding driven by hydrophobic interactions, cluster together to avoid hydrophilic groups/molecules

** Hydrophobic core (nonpolar aminos), hydrophilic shell (polar aminos)

solvent molecules free to interact with polar aminos, increases entropy=favorable

Question 551

Protein denaturation

Answer 551

Loss of non-primary protein structure

• does not break up primary structure!!! unfolded chain of aminos

Primary structure much harder to disrupt than higher-level structure

• Held together by peptide bonds which are covalent bonds between nitrogen and carbon atoms
  
  • intramolecular bonds stronger than intermolecular forces
    
    • sec structure = H-bonds, tert/quat = non-covalent side chain interactions, disulfide bonding

Question 552

Denaturing Agents (proteins)

Answer 552

Temperature extremes

• high temp disrupts non primary interactions, can render protein non-functional
• low temp can decrease protein/enzyme activity, decrease in collisions
  
  • human proteins optimized for body temp

pH extremes

• disrupt charge based interactions in tert/quat structure
  
  • salt bridges form due to ions opposite charges, high or low H+/OH- conc in pH can change these

Detergents (like soaps)

• part polar/part nonpolar disrupts hydrophobic interactions
• SDS used in SDS-page

Reducing agents

• disrupts covalent bonds b/w sulfur atoms (disulfide bonds) via reduction, reforms SH group

Specific compounds

Heat- irreversible

Urea- reversible when urea is gone

Question 553

What is capable of breaking protein primary structure

Answer 553

Protease enzymes

• catalyze hydrolysis of peptide bonds

Often grouped by catalytic mechanism

Favor cleavage at specific sites on target protein - like trypsin

• aminopeptidases cleave from N-terminal
• carboxypeptidases cleave at C-terminal

Question 554

Flow of electrons

Answer 554

Electrons flow from electron rich areas (like oxygen in H₂O) to electron poor areas, driven by their physical properties

• electrostatic attraction between pos and neg and repulsion between neg and neg

Electron rich = nucleophile, electron poor = electrophile

Question 555

Electrophile

Answer 555

Electrophile: short on electrons, wants more

• positive or partial positive charge

strong electrophile really wants more, positive charge or empty orbital

• _​_carbocations or hydrogen ions, aluminum chlroide (AlCl₃) is neutral with empty orbital

weak electrophile has partial positive charge, generally due to induction of more electronegative atoms

• carbonyl carbon has electron density drawn away by oxygen

Electrophiles –> accept electrons –> lewis acids

Question 556

Site vs. Species (electrophiles and nucleophiles)

Answer 556

Electrophilic or Nucleophilic site: refers to the exact location, usually an atom, that acts as electrophile or nucleophile

Electrophilic/Nucelophilic species: shorthand way of denoting which molecule has relevant electrophilic or nucleophilic site, without being overly exact

Question 557

Nucleophiles

Answer 557

Donate a pair of electrons to another species to form a covalent bond

• has lone pairs
• pi bonds (double/triple bond) can act as nucleophile

Can be strong- negative charge

weak- neutral with lone pair or pi bond

Case to case basis, NH₃ is neutral but a strong nucleophile due to hydrogens not pulling electron pair from N atom

Nucleophiles attack electrophiles, donate electrons –> lewis bases

Question 558

Nucleophilic substitution

S_N1 vs. S_N2

Answer 558

Nucelophile replaces other functional group (leaving group)

S_N1: Reaction rate depends on concentration of ONE reactant (the electrophile)

• Rate = k[A]

S_N2: Reaction rate depends on both reactants

• Rate = k[A][B]

Question 559

Nucleophilic substitution

S_N1

Answer 559

Two steps:

1. Leaving group leaves, generates carbocation (slow)
   
   1. carbocation formation = rate limiting step
      
      1. ​depends only on concentration of substrate, reason rxn rate only depends on electrophile
2. Nucleophile attacks
   
   1. often molecule of water or alcohol, will become positive
   2. next step is to deprotonate

Not stereosensitive, can attack from front or back –> equal conc of S and R enantiomers

• Racemic mixture of products

Question 560

Good vs. bad leaving groups

Answer 560

Good leaving group:

• stable in solution after leaving – does not promote reverse rxn
  
  • like water in aqueous soln
    
    • also has positive charge which helps it leave (OH₂⁺)
    • many times want to protonate hydroxyl
  • halogens:
    
    • ​I > Br > Cl > F

Question 561

Nucleophilic substitution: S_N2

Answer 561

Nucleophile and electrophile involved in rate-limiting step; rxn rate depends on both their concentrations

No carbocation is formed, weaker electrophiles

• most common substrate is alkyl halide (tert, sec, or primary)
  
  • Carbon attached to halogen has partial positive charge

1. Nucleophile must attack opposite (back-side) of leaving group (halogen)
   
   1. both nucleophile and leaving group are electron rich
   2. substrate chirality is inverted (ex. S–> R)

Question 562

Predicting S_N1 reactions

Answer 562

Both can co-occur in same rxn, one is usually dominant

For Sn1, increased carbocation stability makes it favorable

• 3° > 2° > 1° = number of alkyl substituents, each makes carbocation more positive
  
  • must be tert or sec for Sn1 to occur

Nucleophile strength not very important for Sn1, but solvent is important

• polar protic solvents: polar and can form H-bonds, highly electronegative
  
  • water, alcohols
  • stabilizes carbocation and interacts with leaving group

Question 563

Sn2 reaction conditions

Answer 563

Driving force: nucleophilic attack

• nucleophile must be strong and be able to reach electrophilic carbon on substrate
  
  • nucleophile must also be non-bulky to avoid steric contraints
  • also non-bulky substrate

Reactivity order: 0’ (methyl) > 1’ > 2’ > 3’ (opposite of Sn1)

Polar aprotic solvents preferred: polar but lacks acidic hydrogens (can have other hydrogens)

• acetone and DMSO, don’t affect nucleophilicity like protic solvents

Question 564

Hydrolysis

Answer 564

How peptide bonds are broken down; nucleophilic substitution rxn

• water is nucleophile to cleave bonds, inserts itself

Opposite is dehydration-condensation rxn

Also the reverse of fischer esterification

Question 565

Fischer esterification

Answer 565

Acid catalyzed subsitution rxn that takes place at carbonyl carbon

• carboxylic acid into an ester
  
  • OH group is replaced by OR group which is an alcohol
• Takes place in presence of strong acid like HCl or H₂SO₄

*Can be reversed = hydrolysis

_{Don’t need to memorize}

1. Acid protonates carbonyl oxygen, resonates and makes carbonyl carbon more electrophilic
2. Alcohol acts as nucleophile and forms tetrahedral intermediate
3. Goal is to eleminate either one of hydroxyl groups, which must be protonated first by acid presence
   
   1. Other hydroxyl reforms carbonyl with its H+, kicking off H₂O⁺
4. Deprotonation

Question 566

Imine formation

Answer 566

Substitution rxn: electrophilic substrate must have carbonyl carbon NOT part of carboxylic acid group

• commonly ketones

Nucleophile is an amine (contains N with lone pair)

• Acid catalyzed, carbonyl oxygen replaced by nitrogen (C to N double bond)
  
  • similar to Fischer esterification

Question 567

Elimination reaction

E1

E2

(not heavily tested)

Answer 567

Leaving group leaves without nucleophilic addition

• new C=C double bond forms

E1: 2 steps, Rate = k[A]

• carbocation formation, alkyl halides
• Bronsted lowry base (proton acceptor) pulls off H from carbon and leaving group leaves
  
  • leaves behind electron pair which forms double bond
• Can be weak base

E2: 1 step, Rate = k[A][B]

• Base attacks hydrogen adjacent to carbon of leaving group, crashes down to form double bond
  
  • kicks off leaving group
• Requires strong base

Question 568

Nucleophilic addition

Answer 568

Nucleophile just adds itself to compound, no leaving group

Requires electrophile with double or triple bond: carbonyl, nitrile, alkene, alkyne

• Focus on alcohol attacking aldehyde or ketone forming hemiacetal or hemiketal
  
  • ​can be catalyzed by either acid or base
  • Tetrahedral intermediate is stable

Acid catalyzed: strong acid protonates carbonyl oxygen making electrophile stronger, then alcohol attacks carbonyl carbon

Base catalyzed: nucleophile made stronger by deprotonation (strong base deprotonates alcohol), attacks electrophile

• if too much alcohol conc, another can attack and form an acetal/ketal

Question 569

Why is nucleophilic addition important

Answer 569

Drives cyclization of monosaccharides from linear form

• alcohol group on linear chain attacks carbonyl carbon of ketone or aldehyde

When two sugars come together to form a disaccharide, glycosidic bond forms between them

Question 570

Tautomerism

Answer 570

Tautomers: two structures of a molecule that can easily interconvert at equilibrium

Does not equal resonance (electron delocalization)

Tautomers entirely different and interconvert by breaking/forming bonds

• aldehyde or ketone and enol interconvert; enol (ene and ol) has C=C double bond and -OH group

Enamines and imines

Amides and imidic acids

Question 571

Keto-enol tautomerism

Answer 571

Ketone/aldehyde interconvert with enol (-ene and ol, C=C and OH group)

• different mechanisms for acidic and basic conditions

Both must have one acidic alpha hydrogen that can be removed by a base

• alpha hydrogen: any hydrogen connected to a-carbon (carbon next to carbonyl carbon)

With asymmetric ketones, there can be multiple products where double bond forms – depending on thermodynamic vs. kinetic

Question 572

Acid catalyzed keto-enol tautomerism

Answer 572

Starting w/ acetone = ketone

1. Strong acid like H₂SO₄ protonated carbonyl oxygen
   
   1. goal is to remove positive charge this creates on the O
      
      1. 2. H₂O acts as weak base and removes one acidic a-hydrogen
   2. electrons in its bond stay behind, form a double bond with carbonyl carbon
      
      1. 3. Carbonyl double bond pushes up lone pair two oxygen, which now has two lone pairs

Question 573

Base catalyzed keto-enol tautomerism

Answer 573

Starting with acetone ketone and NaOH strong base

1. Base can attack a-hydrogen directly, forming double bond with carbonyl carbon and a-carbon
   
   1. puts negative charge on carbonyl oxygen, which picks up proton from water molecule formed in first step

Base OH is not consumed, only participates

Question 575

Enol stability

Answer 575

in aqueous soln, 99% keto and 1% enol

• Factors that can stabilize enol form:
  
  • resonance: phenol is aromatic, more stable than keto form
    
    • • H-bonding: protic solvent can stabilize enol form

Question 576

Resonance of enolates

Answer 576

Enolate anion created as intermediate in base-catalized keto-enol tautomerism

• negative charge on carbonyl oxygen can shift to a-carbon
  
  • Enolates can act as nucleophiles; carbon acts as nucleophile

** rarely see negative charge on carbon

Question 577

Kinetic vs. thermodynamic enolates

Answer 577

Kinetic

• formed most quickly; less stable long term
• Rapid, irreversible
• Low temperature
• strong bulky base
  
  • double bond forms at less substituted a-carbon because less hindered

Thermodynamic

• double bond b/w carbonyl carbon and more substituted a-carbon
• form less quickly, more stable long-term
• high temp
• weaker, less hindered base

Question 578

Aldol Condensation

Answer 578

Two molecules of aldehyde or ketone condense through nucleophilic attack to form an aldol: aldehyde or ketone and alcohol

• can be under acidic or basic conditions, basic is more common
• ** aldehydes and ketones can act as nucleophiles and electrophiles

Cross Aldol condensation: between two diff aldehydes or ketones, or an aldehyde and ketone – unpredictable and tons of products

Many different products

***Alpha beta unsaturated products suggest aldol condensation

*** number carbons when asked for major product

*** can happen backwards

Question 579

Base-catalyzed aldol condensation

Answer 579

1. Strong base removes alpha hydrogen –> enolate
2. Enolate attacks carbonyl carbon of another aldehyde which forms C-C bond
3. Neg charge on oxygen product gets protonated and forms aldol

In many reactions, aldol isn’t final product

1. Spontaneous dehydration can removes OH group
   
   1. base removes a-hydrogen from same a-carbon causing double bond b/w a-carbon and carbon with hydroxyl group, kicking it off
2. Forms a,B-unsaturated aldehyde

Question 580

Acid catalyzed aldol condensation

Answer 580

1. Enol formed through keto-enol tautomerism
   
   1. C=C bond in enol used as nucleophile
2. Second aldehyde prepared to be electrophile by protonating its carbonyl oxygen
3. Enol double bond attacks electrophile carbonyl carbon, forms bond b/w a-carbon of enol and carbonyl carbon of electrophile
   
   1. forms aldol

usually is then changed into a,B-unsaturated aldehydes

Question 581

Michael addition

Answer 581

Aldol condensation can give rise to a,B-unsaturated products

• name implies double bond between a and B carbons adjacent to carbonyl carbon
  
  • nucleophiles can add to carbonyl carbon AND beta carbon due to resonance

1. Michael addition: enolate attacks BETA carbon
   
   1. alpha carbon is protonated
2. Results in two carbonyls separated by 3 carbons

Question 582

Robsinson annulation

Answer 582

Michael addition followed by aldol condensation

1. strong base forms enolate by pulling a-hydrogen from a-carbon
2. Negative alpha carbon nucleophilic attack at other carbonyl
   
   1. forms cyclic structure
3. Aldol condensation dehydration rxn pushes off OH via elimination which forms new C=C double bond

Forms six membered ring with applications in synthesizing steroid hormones and certain drugs

Question 583

Coulomb (C) unit definition

Coulomb’s Law

Answer 583

amount of charge carried by a current 1 ampere in 1 second (A x s)

• elementary unit of charge = e :
  
  • charge of proton and electron = +- 1.602 x 10^-19 C

Coulombs law: calculates force charges exert on eachother

• F = k (Qq / r²)
  
  • • q is test charge, Q is source charge (helps for thinking about electric fields)
  • r = distance b/w charges
  • k = coulombs constant

**attractive forces decrease with the square of distance

Question 584

mass

Answer 584

quantitative measure of inertia, a fundamental property of all matter. It is, in effect, the resistance that a body of matter offers to a change in its speed or position upon the application of a force

weight = mg

m = density x volume

F = ma

Question 585

Resistivity and Conductivity

Answer 585

High resistivity (low conductivity): charge doesn’t readily flow through substance (high þ)

• insulators

High conductivity: charge readily flows (high σ)

• Conductors
  
  • favor conduction: large area, short length
• resistivity and conductivity are a spectrum

Opposite charges attract, like charges repel (pos and neg)

Question 586

Electric Field

Answer 586

Any single point charge can exert a force on any other single point charge

magnitude of an electric field =

• force experienced by charge / magnitude of charge
• E = F/q
  
  • ​
  • q = test charge, charged particle used to test magnitude of field at any given point

E = kQ / r² (combines coulombs law, Q = source charge)

Similar to gravitational field

• shows field strength changes with distance

Question 587

Electric Field Lines

Capacitors

Answer 587

Arrows point in the direction that a positive test charge would travel in an electric field

• away from pos charge, toward neg charge

capacitors- linear charged plates that create an electric field between them

Question 588

Torque

Answer 588

Force that causes rotation

T = Fd sin (0)

Question 589

Electrical work definition = electric potential energy

Electric Potential

Answer 589

Electric potential energy = U = kQq / r

Work is in Joules, also the unit for energy

Electric potential = V (volts) = U / q = Joules / Coulombs

• q = test charge
• Volts are a measure of how much energy is needed to move a certain amount of charge to a certain point in an electric field
  
  • if movement is spontaneous, how much energy is released

Not the same thing! electric potential normalized for charge

Question 590

Equipotential lines

Voltage

Answer 590

Connect all points with same electric potential

• perpendicular to field lines

Voltage: Electric potential difference between two points on different equipotential lines

• ∆V = ∆U / q

No work done by or against an electric field when moving charged particle along equipotential line

Question 591

Magnetism

Diamagnetic, paramagnetic, ferromagnetic

Answer 591

Produced by the spin of elementary particles (electrons)

• electrons have spin of +1/2 and -1/2
  
  • magnetic dipole moments that cancel out in full orbitals
• diamagnetism: **materials with only paired electrons do not generate a magnetic field
  
  • water, wood, fabric
  • weakly repelled by magnets

Paramagnetic: unpaired electrons have random spins, material as whole have no net dipole

• weakly attracted by magnetic fields
• external field can temporarily fix electron spins and create magnetic polarization

Ferromagnetic: unpaired electrons have stable nonrandomized electron spin – permanent magnets

Question 592

Magnetic dipoles

Answer 592

Basic unit of magnetism, like charge for electricity

• every magnetic dipole has a north pole and south pole
  
  • ​opposites attract
  • north can’t exist isolated without south, vice versa

Question 593

Magnetic fields (B)

What is their unit, how do their lines run, what are some conditions

Magnetic field equation shows:

Answer 593

Magnetic field lines run from north to south (electric run from pos to neg)

• strength of magnetic field in Teslas (T)
• Tesla: magnitude of magnetic field at which a particle with a charge of 1 coulomb moving perpendicularly at 1 m/s experiences force of 1 Newton
  
  • *large unit of force

** magnetic fields only exert force on moving charges, moving charges also generate magnetic fields

Strength of magnetic field directly proportional to current, inversely (but linearly) proportional to distance from current

B = u I / 2πr (u = permeability of free space, I = current, r = distance)

Question 594

Directionality of magnetic field

Answer 594

Direction of field around current carrying wire determined by right hand rule

• “hold” wire with right thumb pointing in direction the current is flowing and fingers curl around in direction of magnetic field
  
  • opposite direction of electron flow

circle with X = field going into page

circle with dot = field coming out of page

(think of an arrow)

Question 595

Magnetic force equation

what it implies

Answer 595

F_B = q v B sin0

• F_B = force exerted by magnetic field (vector, has magnitude & direction)
• q = charge of particle
• v = velocity (vector)
• B = strength of the magnetic field
• Theta 0 = angle of velocity of particle to magnetic field

Important: force directly proportional to charge and strength of magnetic field; if any of these values are zero, no force from magnetic field

• **For force, particle must be charged and moving and magnetic field must have strength

**Sin(0) means maximum force when moving perpendicular, 0 when moving parallel

Question 596

magnetic force for current carrying wire

determining directionality of vectors

Answer 596

F_B = I l B sin(0)

I= current in Amperes (C/s)

l = length of wire (m)

Directionality- second right hand rule

Question 597

Electromagnetism (lorentz force)

Answer 597

A summation of the forces exerted on a charge by electric and magnetic forces

Question 598

Ohm’s Law

Current =

Direct Current =

Answer 598

Ohms Law: V = I R

• ohms= volts / amperes

Current follows the movement of positive charge (not movement of electrons)

Current = charge/ time

• in Amperes (C/s)

Direct Current: current that moves in a single direction through a circuit

Question 599

Resistance

Answer 599

Resistivity described by Rho (p) and conductivity described by σ, material specific constants for given temperatures

• describe degree to which physical material resists/conducts current
• inverse concepts

resistance (R) = p (l / A)

conductance (G) = σ (A / l)

• large area and short length favor conduction

Question 600

Circuit components:

What makes current move?

Answer 600

• Resistors: resist moving charge
  
  • kind of like friction, allows current to be changed to heat or light
• Capacitors: store charge
• Conductive wire

What makes current move? Voltage, electric potential difference between two points that charges flow spontaneously across

• current flows from positive point of voltage to negative (current positive wants to go to negative)

*** voltage differential that powers a circuit (usually in battery) is called the electromotive force (EMF)

• Long line= +
• short line = -

Question 601

Power

Power dissipated by a current

Answer 601

Rate at which energy is used or produced

• Power = Work/ Time (J/s)
• Power dissipated by a current = P = IV
  • **can factor ohm’s law into equation V = IR

Derivation:

Volts- electric potential energy of a charge at a given point in an electric field, divided by the magnitude of that charge

• V= U / q
  
  • • Work = ∆U (change in electric potential of energy)

Question 602

Activation energy (E_a)

Answer 602

For a reaction to take place, activation energy threshold must be overcome– Represents transition state , high energy and unstable

• Reactants –> transition state –> products
• Determines how quickly a reaction will proceed – kinetics

Question 603

Chemical Kinetics refers to

For a reaction to occur:

Answer 603

Chemical reaction rates – controlled by activation energy and temp.

Reactants must collide with each other in specific orientation and with sufficient kinetic energy –>

• transition state: formation of unstable intermediate

Question 604

How to lower E_a

Answer 604

Lowering Ea done by deploying catalysts (enzymes)

• stabilize transition state
• weaken bonds within reactants
• changing orientation to elicit effective collisions
• increasing frequency of collisions
• donating electron density to reactants

Enzymes don’t affect thermodynamics: Gibbs free energy, enthalpy, entropy

Catalysts not consumed, small amount can greatly affect products

Question 605

Heterogenous vs. Homogenous Catalysis

Answer 605

Based on the phase of catalyst compared to phase of reactant species

heterogenous catalyst: in different phase than reactants

• typically catalyst is solid and reactants are liquid/gas
• based on surface area of catalyst, grinding it into a powder more efficient

homogenous catalyst: same phases

Question 606

Rate of a Chemical Reaction defined as

Expressed mathematically by:

• Reaction order:

Answer 606

Disappearance of reactants over time/appearance of products (Molarity/sec)

• Molarity= moles/L

expressed mathematically by Rate Law: relationship b/w reactant conc. and rate of rxn

• rate= k[A]^x[B]^y
  
  • • where x and y denote rxn order w/ respect to A and B
  • order: degree to which rate of rxn is dependent on reactant
    
    • sum of reactants orders give overall order (x+y)

Question 607

Reaction order:

Answer 607

Degree to which rate of rxn is dependent on each reactant (rate = k[A]^x[B]^y

• overall order is sum (x+y)

Zero order = [A]⁰[B]⁰ ; rate doesn’t depend on reactants

*Rate law only includes reactants that determine rate, can be others

Question 608

How to find rate law (elementary rxns, multi-step rxns)

Initial rates method

Rate constant (k)

Answer 608

In one step elementary rxns, coefficients of reactants are their orders

In multi-step rxns, found by slowest/rate-limiting step

• determined experimentally with trials, one Reactant conc changes while other stays the same
  
  • compare the rate to the conc using rate equation and solve for the order (reference pic)

Units of k vary depending on overall order:

k = rate / [A]^x[B]^y

^{To find units, just plug in what you know and solve for k}

Question 609

How are zero order reactions possible?

What do first order reactions consist of?

Second order?

Answer 609

Zero order reactions: unaffected by changes in reactant concentrations

• ex. enzyme catalyzed reactions in which enzyme is saturated.
  
  • reactant concentrations far exceed available active site

First order: radioactive decay or S_N1 reactions

Second order: physical collisions between two reactant molecules

Question 610

Simple circuits: how does current flow?

How is ∆V= IR applied (ohm’s law)

Answer 610

Current flows from high voltage to low voltage (- towards +)

• voltage drop isn’t distributed evenly across circuit

∆V = IR can be applied to circuit as a whole as well as components

• can apply to resistor(high voltage drop) and conductive wire (has no voltage drop)

Question 611

Resistors in Series

Resistors in Parallel

Answer 611

Resistors in series: added one after another, no junctions

For a circuit with 3 resistors in series:

• I_total = I₁ = I₂ = I₃
• _Vtotal = v₁ + v₂ + v_3​
  
  • ***voltage drops in circuit have opposite sign as EMF
• R_total = R₁ + R₂ + R₃

Resistors in parallel: current is split, branches into different resistors

3 resistors in parallel:

• I_{total =} I₁ + I₂ + I₃
• **V_total = v₁ + v₂ + v₃
• 1/R_total= 1/R₁ + 1/R₂ + 1/R₃

Question 612

Kirchhoff’s Laws (circuits)

Answer 612

1. Kirchhoff’s first law: I_total = I₁ + I₂ + I_{<strong>3… </strong>}
   
   1. _​The sum of current entering a junction must equal the sum exiting the junction
      
      1. 2. Kirchhoff’s second law: v_{total =} v₁ + v₂ + v₃
   2. _​The sum of the voltage drops throughout the circuit is equal to source voltage (EMF)

Question 613

Ammeter measures…

Voltmeter measures…

Ohmmeters measure…

Answer 613

Ammeter measures current (in amperes)

• inserted in series, has zero resistance

Voltmeter calculates voltage

• inserted in parallel
• has known resistance, ideally uses least amount of current possible
  
  • since resistance added reciprocally in parallel, has little effect

Ohmmeters measure resistance

• has known resistance, uses little current

Question 614

Capacitors

Answer 614

Devices that store electrical charge, two physically separated components where opposite charges are accumulated

• parallel, flat, thin, conductive plates separated by nonconductive insulated material (dielectric)
• accumulation of charge is due to voltage applied

*

Question 615

Capacitance (C)

equation

Dielectric constant

Answer 615

capacitance: degree to which a capacitor can store charge

• C = Q / V amount of charge stored given a voltage
  
  • in farads which is 1 coulomb/ 1 volt

Depends on area of conductive plates and dielectric material (insulator between them, the better the insulator the more charge that can be builtup)

C = Σ₀ (A/d)

• Σ₀= permitivity of free space (in a vacuum)
• A= area (bigger area, higher C)
• d= distance b/w plates (smaller distance, higher C)

K= dielectric constant = Σ_{m /} Σ₀

• every insulator has higher permitivity than Σ_{0 (vacuum)}
• The greater K, the more charge it can store

Question 616

Properties of capacitors

Answer 616

1. Create uniform electric fields, strength of which is defined by E=v/d
   
   1. ​ eqn only applies to uniform fields
      
      1. 2. Store energy in the form of the electrical field that they generate which is potential energy
   2. PE = 1/2 CV²
2. Capacitors in series add reciprocally, capacitors in parallel add directly
   
   1. _​_Opposite from resistors

Used for defibrillators, **electrical potential difference across cell membranes (usually -70 mv)

Question 617

Reversibility in reactions

Haber Process (reversible rxn)

Answer 617

Reaction can progress forward and in reverse

• majority of reactions in chemistry
• irreversible only progress forward

1 N₂ + 3 H₂ = NH₃ (ammonia)

Question 618

Equilibrium

Answer 618

Forward and reverse reaction rates are equal

• Does not mean reactant and prodct concentrations are equal, but they are stable

THERMODYNAMICS- if spontaneous rxn, favors products and equilibrium will have higher product conc

• nonspontaneous favors reactants

at Equilibrium, entropy is maximiazed and ∆G = 0, stays at equilibrium unless disturbed

Question 619

1. Factors that affect equilibrium constant K_eq
2. K_eq of reverse reaction =

Answer 619

1. Temperature affects K_eq value
   * Factors that don’t: amount of concentration, presence of a catalyst (impacts kinetics)
2. K_eq of reverse rxn is 1/Keq3.

Question 620

The Reaction Quotient (Q)

Answer 620

Reaction quotient tells us if given concentrations are at equilibrium

• aA + bB = cC + dD
• Q = [C]c[D]d / [A]a[B]b

Shows which direction reaction proceeds toward equil

• low Q means reactants dominate mixture, high Q means products do

Must be compared to K_eq

• Q < Keq : less product than it should at equilibrium, rxn goes forward
• • Q > K_eq : reverse direction towards reactants
• • Q = Keq is at equilibrium

Question 621

Le Chatelier Principle

How reaction mixtures respond when shifted from equilibrium

Answer 621

Stress = change in reactant/product concentration, change in temperature, pressure, volume causes a shift toward reactants (left) or towards products (right)

• If A + B = C and additional “A’ is added, reaction shifts to the right and more “C” is formed
  
  • less B concentration at equilibrium than before
• Concentrations fix themselves proportionally to Keq value in equation
  
  • Keq = [C]/ [A][B]

Removing product as its formed can increase reaction yield for the product

Question 622

How to make the most Acetylsalicyclic acid (ASA) during synthesis

(Aspirin)

Answer 622

1. Excess reactant (acetic anhydride) to drive rxn toward products
2. Removal of product after its synthesized

Question 623

What is a solution

Solutions can be…

Answer 623

A homogenous mixture

• mixture: 2+ substances where substance remains its own identity
  
  • can be homogenous- uniform composition
  • or heterogenous- uneven distribution
    
    • sand at the bottom of a glass

Solutions can be gaseous, liquid, or solid; in chemistry usually is solid molecules dissolved in liquids

Question 624

Dissolution

Solvation

Answer 624

Dissolution: Act of dissolving

• solute (minority compnent) is dissolved in/interacts with particles in the solvent (majority component)
  
  • solvent separates solute molecules or breaks ionic molcules into ions

Solvation: abundant individual solvent particles surround solute particles

• like dissolves like

Question 625

Saturated solution

Unsaturated solution

Supersaturated solution

Answer 625

Extent to which solute can be dissolved in a solvent

saturated solution: maximum amount of solute that can dissolve in given solvent has been added

• adding more solute will form a precipitate

unsaturated solution: contain less than maximum amount of solute

supersaturated solution: more than max amount of solute dissolved in solution

• higher temperature when dissolved, cool very slowly and it will remain
  
  • crystallization: adding more solute once solution cooled, excess solute crystallizes

Question 626

Solubility vs. Ionization

Answer 626

Solubility: the extent to which a substance dissolves in a solvent

Ionization: dissolution of ionic compounds

• Ionic compounds DO ionize when they dissolve in solution

Question 627

Electrolyte

Answer 627

Dissolution of ions results in charged species in water

• Ions in solution conduct electricity

Question 628

Effect of temperature and pressure on solubility (for gases and solids):

Answer 628

Temp: for solids, higher temp = higher solubility depending on if reaction is endothermic or exothermic

Gases more soluble in liquids at lower temperatures

• _​_Dissolved O₂ content in bodies of water is higher during winter than summer

Question 629

Solubility Rules (what compounds are always soluble)

Answer 629

**most important, “absolutes”

1. **All alkali metals (Li+, Na+, K+, Rb+, Cs+, Fr+) and ammonium salts are soluble
2. **All nitrates (NO₃^-), chlorates (ClO₃^-), and acetates (CH₃COO^-) are soluble
3. Halides (Cl^-, Br^-, I^-) are soluble
   * unless combined with lead, mercury, silver
4. Sulfates (SO₄^2-) are soluble
   * except with calcium, strontium, barium, lead, silver
5. Carbonate (CO₃^2-), phosphate (PO₄^3-), sulfide (S^2-) and sulfite (SO₃^2-) are insoluble
   * except with alkali metals
6. Hydroxides and metal oxides are insoluble
   * except with alkali metals, Ca, Sr, or Ba

Question 630

Concentration in a solution can be expressed in 3 ways:

Answer 630

Molarity: (M) moles of solute / liter of solution (M/L)

• 1 mM = 1/1000L

Molality: (m) moles of solute / kg of solvent

• 1L of water = 1 kg
• more impact in higher solute conc (affects the volume)

Normality: (N) number equivalents of solutes per 1 liter of soln

• for acid/bases, equivalents are H+ and OH-

Question 631

Colligative Properties (4)

Answer 631

Properties changing solely due to concentration of solute in solution

** Does not depend on identity of solute, depends on total number of dissolved solute particles

• ex. adding salt to water raises its boiling pt, lowers its freezing pt

Freezing pt depression

Vapor pressure reduction

Boiling pt elevation

Osmotic pressure

Question 632

How to calculate normality (N) (in acid base context)

Answer 632

Normality of acid (N) = molarity of acid x number of protons per molecule

Normalitu of base (N) = molarity of base x number of hydroxide atoms

Question 633

Solubility Constant (Ksp)

Answer 633

Ksp = [C]^c[D]^d / [A]^a[B]^b

Follows exact same rules of Keq

MgCl_{s (s)} + H₂O _(l) = Mg²⁺_(aq) + 2Cl^-_(aq)

• K_sp = [Mg²⁺][Cl^-]²

** high Ksp means high conc of dissolved ions compared to initial solid, high solubility

**low Ksp means low solubility of initial solid, insoluble

also a Q value for concentrations not at equilibrium

Question 634

Molar solubility

Answer 634

Number of moles that need to dissolve for a soln to be saturated

Question 635

Common Ion Effect

Answer 635

Solubility of an ionic species decreases when one of its component ions (common ion) is already present in solution

• the higher the conc of common ion, the less solute that can dissolve before Ksp is reached

Example of Le Chatilier Principle

AgCl —> Ag + Cl

Ksp= [Ag][Cl]

If Cl goes up, Ag goes down to equal Ksp value

Question 636

Coordination Complex/ complex ion

Answer 636

Helpful with common ion effect

Ions can form different molecules in solution that will take away its concentration from that of the solubility Ksp equation

Question 637

Acid Base chemistry and common ion effect

Answer 637

H+ and OH- can be common ions if present in solution with an ionic species that contains them

• the more basic a solution, the lower the solubility of a molecule like NaOH

A base added to an acidic soln ionizes more

An acid added to a basic soln ionizes more

MCAT can use wording like base or pH to imply common ion effect

Question 638

1. Arrhenius acid bases (earliest)
2. Bronsted Lowry
3. Lewis

Answer 638

1. Arrhenius: Acids and bases dissociate to form different ions; Acids form H+, Bases form OH-

• acids must contan H+, bases must contain OH-
  
  • *NH₃ is a common base without OH group
• not very broad

2.*** Bronsted Lowry: Acid is a proton donor (loses H+), Base is a proton acceptor (gain a bond to H+)

• after acid loses its proton = conjugate base
• when base gains a proton = conjugate acid
• typically what MCAT refers to if not specified

3. Lewis: acids are electron acceptors, bases are electron donors

• most inclusive definition

Question 639

Amphoteric Species

Answer 639

Can either accept or donate a proton (acid and base)

• water, amino acids

Question 640

Acid base equilibria

Kw, Ka, Kb

Answer 640

Equilibria of reactions in which protons are gained/lost

1. ** protons exist as H₃O+ in solution (hydronium)

K_w: equilibrium for auto-ionization of water (Kw= [H₃O+][OH-])

• equilibrium strongly favors reactants, H₂O
• 1 x 10^-14 at 25 deg C, larger at higher temp
• 1:1 ratio of H₃O and OH

Ka: acid dissociation constant

• Ka = [H+][conj base]/[acid]. ** high Ka dissociates more readily
  
  • low Ka acid dissociates less readily

Kb: base dissociation constant

• high Kb means base dissociates readily

Question 641

If pH is 8 and H₃O+ and OH- concentrations are equal (like water at 0 deg celsius)…

Answer 641

The solution is still neutral

Pure water is neutral at any temp

*** pH of 7 is only neutral at standard state temp

Question 642

Acid-Base strength tells us…

Strong acid properties

Answer 642

How readily acid/base dissociates in reaction

• strong acids:
  
  • ionize fully in water
  • have large Ka values
  • tend to produce soln with low pH
• • strong bases:
    
    • ​ionize fully in water
    • large Kb values with high pH

Question 643

Strong acids to memorize

Answer 643

HI. Hydroiodic acid

HBr. Hydrobromic acid

HCl. Hydrochloric acid

HNO₃ Nitric acid

H₂SO₄ sulfuric acid

HClO₃, HClO_4. chloric acid, perchloric acid

3 M HCl = 3 M H₃O+

Question 644

Strong bases to memorize

Answer 644

Hydroxides of alkali or alkaline earth metals, like NaOH, KOH, Ca(OH)₂

NH₂-

H^- hydride

CH₃O^-

CH₃CH₂O^-

(CH₃)₃CO^-

methoxide, ethoxide, tert-butoxide

**assume all other bases weak.

Question 645

Equations

pH and pOH

pKw, pKa, pKb

Answer 645

“p” stands for negative log; pH = -log[H+]

pOH = -log[OH-]

pKw = -logKw = pH + pOH = 14 **at 25 deg C

• **pKa + pKb = pKw = 14

pKa = -logKa

• pKa get smaller as Ka gets bigger

pKb = -logKb

• pKb gets smaller as Kb gets bigger, stronger base

Ka x Kb = Kw

Acid and its OWN conjugate base

• If acid A > acid B, conj base A < conj base B
  
  • acid A likes to give up proton more, will have more stable conj base (doesn’t want to pick back up proton)

Question 646

Acid naming

Answer 646

• Named depending on if:
  
  • Organic: compounds with carbon-hydrogen bonds
    
    • carboxylic acids: propanoic acid
    • -oic acids
  • Inorganic: don’t contain oxygen
    
    • like HI, HBr
      
      • Hydro + -ic acid
        
        • hydroiodic acid
  • Oxyacids: inorganic acids with oxygen
    
    • name depends on # of oxygen atoms
    • -ic corresponds to -ate anion
      
      • HClO₃ = chloric acid
    • _+1 oxyge_n = per-
      
      • perchlorate = perchloric acid
    • -1 oxygen = -ous
      
      • Chlorite = chlorous acid
    • -2 oxygen = hypo- and -ous
      
      • hypochlorite = hypochlorous acid

Ate to ic

Question 647

Colligative property: Vapor pressure reduction

Equation

Answer 647

If a liquid is exposed to air, some will evaporate into a gas until gas and liquid phases reach equilibrium; increases with temp

• pressure exerted by gas above liquid is vapor pressure

Adding solute to liquid reduces amount of gas produced

• attraction between solvent and solute particles
• surface composed of solvent and solute, less surface area for solvent to evaporate
• solutes must be nonvolatile (don’t evaporate readily)

P = X_aP_a​

Vapor pressure in soln = mole fraction x vapor pressure of pure solvent

More solute, more VP of soln

Question 648

Colligative property: Boiling point elevation

Equation

Answer 648

Temperature at which vapor pressure equals atmospheric pressure

Adding solute decreases VP and increases boiling pt

• doesn’t depend on type of solute, depends on number of solute particles

∆T_b = iK_bm

i = ionization / Van’t hoff factor for solute (NaCl = 2)

Kb= constant for solvent

m = molal solute conc (moles solute / kg solvent)(1 for water)

Question 649

Colligative property: Freezing Point Depression

equation

Answer 649

∆T_f = iK_fm

Change is a decrease in freezing point

i = ionization factor

m= molality

Question 650

Colligative property: Osmotic pressure

Answer 650

Pressure required to prevent osmosis: flow of solvent through a semi permeable membrane across concentration gradient, from low solute to high solute

• equalize concentrations

Osmotic pressure stops this flow to counteract osmosis

• used for biological membranes
• depends on total number of solute particles given by ionization factor (i)

π = iMRT

i x molarity x gas constant x temp

Question 651

Buffer function

Equation (henderson-hasselbalch)

half equivalence point is

Answer 651

Solution that resists changes in pH when an acid or base is added

• created from weak acid and conjugate base or weak base and conjugate acid
• highly effective to small to moderate quantities of base or acid

pH = pKa + log₁₀ (A^- / HA)

• pH is pH of buffer and pKa is that of the weak acid
• **pKa = pH when acid is 50% protonated (half equivalence point)
  
  • ​A-/HA = 1 and log₁₀1 = 0

Question 652

What acid base pair is a good buffer?

Answer 652

Acid has a pKa close to desired pH of solution, most effective when amounts of acid and conj base are approx equal

Question 653

Bicarbonate Buffer System

Answer 653

Plays key role in bloods ability to protect against pH changes

CO₂ + H₂O = H₂CO₃ = H⁺ + HCO₃^-

• H2CO3: carbonic acid is weak acid
• HCO3-: bicarbonate is conj base

Blood pH = 7.35-7.45

• even small deviations from this can cause acidic/alkaline plasma which can be fatal

Question 654

Solving buffer problems (ICE)

Answer 654

Buffer has 5 mol HCO₃^- and 5 mol H₂CO₃ in 10 L H₂O

What happens to bicarbonate buffer if 1 mol HCl is added?

• H₂CO₃ Ka = 4.3 x 10^-7

HCO₃- + H⁺ = H₂CO₃ (don’t inclue Cl^-, not acidic)

HCO₃^- H+ = H₂CO₃

Initial 5mol 1mol 5mol

Change. -1mol -1mol +1mol

Equilibrium 4mol 0 mol 6 mol

pH = -log(4.3x10^-7) + log (4/6) = 6.2 (pH went down as expected)

Question 655

Estimating log function

Answer 655

log N = x —> N = 10^x

log₁₀1 = 0 —> 1 = 10^x

log₁₀10 = 1

log 10^-2 = -2

Question 656

Hidden Buffer Question

Answer 656

HBr + NH₃ –> NH₄⁺ + Br^-

1 mol 2 mol 1 mol 1 mol

Not acid and conj base but still a buffer, neutralize each other in 1:1 ratio

Question 657

Neutralization

Equation

Answer 657

When an acid is neutralized, all of the protons from the original acid have reacted with hyroxide ions from added base

• ratio of acid to base is 1:1 in moles
• Monoprotic acid contains only one acidic proton
• Monoprotic base can only accept one proton

M_aV_a = M_bV_b —> for monoprotic acids

• Molarity and volume of acid and base

For diprotic and triprotic acids, have to use normality

Question 658

Normality can be used for…

Equation

Answer 658

Redox rxns, Precipitations, acid-based chemistry neutralization

N = (mol of OH^- or H+ ions) / L solution

• used for polyprotic acids
• for H₂SO_4, N= 2 mol H+/ 1L

*** at neutralization, normality of acid x volume of acid = N of base x V of base

N_aV_a = N_bV_b

Question 659

Titration definition

2 types of titrations

Answer 659

Technique used to find the concentration of a solution of unknown molarity

• solution is placed in a flask and a diff soln of known conc is added drop-wise
  
  • volume of known soln added is used to determine molarity of unknown soln

analyte: soln of unknown conc

titrate: soln of known conc

2 types of titrations: acid base and oxidation reduction

Question 660

Acid-Base Titrations

Indicator

Answer 660

Colorimetric titrations: analyte changes color at equivalence point, point when acid or base has been fully neutralized

• use normality eqn: N_analyteV_analyte = N_titrantV_titrant
• eqn only valid at equivalence pt

Indicator: undergo pH-dependent color changes

• occurs once soln pH > pKa of indicator
  
  • indicator pKa should be close to predicted pH at equivalence point

Question 661

Titration Curves

Answer 661

x-axis is volume base added, y-axis is pH

• Equivalence point is at pH = 7, complete neutraliation
  
  • at this point **, mole equivalents of acid = mole equivalents of base
• Half equivalence point is where half of volume of titrant needed to reach equivalence point has been added
  
  • pH = pKa

When a base is titrated with an acid, the curve is flipped from high pH to low pH

Question 662

Strong acid has ____ conj base

Weak acid has ____ conj base

Answer 662

Strong acids have weak conj bases

Weak acids have strong conj bases

Question 663

Equivalence point of strong acid/strong base titrations have a pH of

Equivalence point of weak acid/strong base

Strong acid titrated with a weak base has pH

Answer 663

Strong acid titrated with strong base equivalence point pH is 7.

Weak acid/strong base equivalence point pH is always above 7

Strong acid titrated with a weak base has a pH below 7

Question 664

Polyprotic Titrations

Answer 664

1st proton lost most readily, has highest Ka value

• 2nd and 3rd are harder to lose because they are bonded to an anion

3 pKa values and thus 3 half equivalence points/equivalence points for an acid with 3 protons (H₃PO₄)

Question 665

Basic and acidic amino acids

Answer 665

Aminos denature at extreme pH values, have optimal values (7.4 in humans)

For proteins, affects tertiary structure

• amine group is basic, carboxylic acid group is acidic
  
  • when peptide bond is formed b/w aminos, amine group is bonded to carboxylic group forming an amide which are neutral
  • this is why when talking about amino acids acid base chemistry, usually referring to their side chains

Basic aminos have a nitrogen containing side chain

• can gain proton to nitrogen to become positively charged conj acid
  
  • **can act as an acid now if in a basic soln

Both acidic aminos have a side chain with carboxylic acid

• all basic and acidic aminos side chains can exhibit basic and acidic properties

Question 666

1. If glycine is put in an acidic solution, what will happen?
2. If put in soln with high pH?
3. At neutral pH (normal body conditions)

Answer 666

1. Protons attach to amino group (NH₃+) and carboxylic acid group (COOH); net charge of +1
2. In a soln with high pH, amine group is NH₂ and carboxylic acid group is COO^-
   * net charge of -1
3. At neutral pH, NH₃+ and COO^- –> neutral which is a zwitterion
   * all aminos have zwitterion forms, but not all exist as them at physiological conditions

Question 667

Zwitterion

Answer 667

Electrically neutral ion with both positive and negative charges

Question 668

multiple pKa’s of amino acids and other compounds

Answer 668

pKa: how acidic a functional group is (likeliness of giving up H+’s)

• lower the pKa, stronger the acid
• **polyprotic acids have multiple pKa values for each proton they can give up
  
  • **most amino acids will have 3, except for ones without acidic/basic side chains like alanine will have 2 (for amine group and carboxylic acid group)

Lowest pKa is 1

Question 669

How are pH and pKa of a functional group related?

Answer 669

When pH is equal to the pKa of a functional group, it will be protnated on exactly half of the molecules in solution

• from henderson hasselbalch equation
• carboxyl pKa: 2
• amine pKa: 9

Question 670

Nonpolar Amino Acid titrations

What type of titration is it?

What is the isoelectric point?

Amino charge at different pH’s?

Answer 670

Each amino acid produces a unique titration curve

Weak acid, strong base titration

• at low ph, functional groups of amino acid all protonated
• at horizontal regions of graph, amino acid soln acts as buffer

***non polar aminos have two pKa values

At half equivalence point 1 (pH 2), half of carboxyl groups deprotonated

• at equivalence pt 1, all of carboxyl groups deprotonated = zwitterions
  
  • **Isoelectric point(pI): pH at which amino acids net charge is 0
    
    • entire peptides and proteins have pI’s
• Half equivalence point 2 is pH 9, half of amine groups deprotonated
  
  • Equivalence point 2 has all of amine groups deprotonated, amino charge of -1

At equivalence point, 1 mol base:1 mol amino, can use to find concentration

Question 671

Acidic, Basic, Polar amino acid titrations

Answer 671

*3 pKa values instead of 2 for nonpolar aminos

• 3 half equivalence points, 3 equivalence points
• pKa₁ =2 (COOH), pKa₂ = 4 (COOH of side chain), pKa₃ = 9 (NH₃)
  
  • pH below 2 has all 3 groups protonated, charge: +1

For acidic aminos(negative): below pH 2, charge is +1; pH between 2 and 4, charge of 0; b/w 4-9 is -1, and pH above 9 is -2

At 1st equivalence point, moles of base added=moles of acid

• this is also the isoelectric point, where molecule is neutral
  
  • for acidic aminos, between two lowest pkas
  • for basic aminos, between two highest pkas

Basic aminos titrated with strong acid; start with +2 charge and end at -1

**MCAT treats polar uncharged aminos as having 2 pKa’s, even with side chain

Question 672

Anatomy of central nervous system

Answer 672

Central nervous system(CNS)- processing sensory info and initiating muscle movement

• brain and spinal cord, both are bathed in cerebral spinal fluid (CSF)
  
  • ​both encased in tough membranes called meninges and protected by skull/vertebrae
    
    • ​meninges consists of 3 layers: dura mater, arachnoid mater, and pia mater

Question 673

Peripheral NS

Answer 673

Dictates all other nerves and nervous tissue, including:

• afferent fibers (periphal neurons) that carry info into CNS
• efferent fibers: carry signals from CNS to periphery
  
  • SAME: sensory afferent, motor efferent
• ganglia: clusters of cell bodies found along sides of spinal cord, in the digestive system, and elsewhere

Question 674

Brain Divisions

Answer 674

During fetal development, the neural tube forms 3 main regions that give rise to the brain: from anterier to posterior (front to back)

1. Prosencephalon - Forebrain
   
   1. ​behavior and personality, develops into diencephalon and telencephalon
      
      1. ​Diencephalon contains:
         
         1. thalamus: relays sensory and motor info, regulates sleep
         2. hypothalamus: regulates homeostasis, communicates between endocrine and nervous systems
         3. Pineal gland and posterior pituitary gland: secrete hormones
      2. Telencephalon:
         
         1. ​cerebrum: largest structure
            
            1. divided into thin outer layer: cerebral cortex (5 lobes)
            2. hippocampus
            3. basal ganglia
2. Mesencephalon - Midbrain
3. Rhombencephalon - Hindbrain- more basic functions that have been highly conserved across species through evolution
   
   1. Cerebellum‘little cerebrum’: coordination of motor control
   2. medulla oblongata: controlls autonomic functions
      
      1. breathing and heart rate
   3. Pons: a relay station for signals b/w cerebellum, medulla, and rest of brain
      
      1. also contains neuron clusters that deal with sleep, respiration, swallowing, taste, bladder control and balance

Question 675

Limbic system structures

Answer 675

Emotion, motivation, memory

• Cingulate gyrus
• Hippocampus
• Amygdala
• Thalamus
• Hypothalamus

Question 676

Cerebral cortex lobes (5 but only need to know 4)

Answer 676

1. Frontal lobe: higher level cognition, executive functions

2. Parietal lobe: sensory processing

3. Temporal lobe: sound and language processing, memory consolidation

4. Occipital lobe: primary visual cortex

Responsible for sensation, perception, memory, cognition

Question 677

Forebrain

Answer 677

Advanced higher-level functions

• ​behavior and personality, develops into diencephalon and telencephalon​
  
  • Diencephalon contains:
    
    • thalamus: relays sensory and motor info, regulates sleep
    • hypothalamus: regulates homeostasis, communicates between endocrine and nervous systems
    • Pineal gland and posterior pituitary gland: secrete hormones
  • Telencephalon: ​
    
    • cerebrum: largest structure
      
      • divided into thin outer layer: cerebral cortex (5 lobes)
      • hippocampus
      • basal ganglia

Question 678

Hindbrain

Answer 678

Hindbrain- more basic functions that have been highly conserved across species through evolution

• Cerebellum‘little cerebrum’: coordination of motor control
• medulla oblongata: controlls autonomic functions
• breathing and heart rate
• Pons: a relay station for signals b/w cerebellum, medulla, and rest of brain
  
  • also contains neuron clusters that deal with sleep, respiration, swallowing, taste, bladder control and balance

Question 679

Midbrain

Answer 679

Motor control, sleeping, homeostatic regulation

• superior colliculus- visual reflexes
• inferior colliculus- auditory reflexes
• substantia nigra- facilitates coordination of voluntary motor control
  
  • affected by parkinson’s disease

Question 680

Parkinson’s disease

Answer 680

Progressive neurodegenerative condition characterized by the loss of dopaminergic neurons in the substantia nigra

Question 681

Brain stem consists of

Answer 681

Midbrain, medulla oblongata, pons

Connects brain to spinal cord

Question 682

Spinal cord

Answer 682

Contains bundles of sensory/afferent neurons that relay sensory info to the brain and motor/efferent neurons that relay info from brain to muscles

• protected by vertebrae

Question 683

Conflict theory

Answer 683

Conflict theory states that tensions and conflicts arise when resources, status, and power are unevenly distributed between groups in society and that these conflicts become the engine for social change.

Question 684

Divisions of Nervous System

Answer 684

Central NS and Peripheral NS

• Central is brain and spinal cord

Peripheral NS is autonomic and somatic NS

• autonomic is divided into sympathetic and parasympathetic
  
  • also enteric: digestion

Question 685

Peripheral NS

Answer 685

Divided into somatic and autonomic, as well as enteric

• somatic nerves: execute voluntary movement innervating skeletal muscles throughout the body
• autonomic NS: controls involuntary responses such as sweating and pupil dilation
  
  • sympathetic: induces fight or flight response under acute stress
    
    • accelerate heart and respiration rates to improve oxygenation of skeletal muscle tissue
    • reduce blood flow to organ systems less essential (digestive tract)
    • dilates pupils allowing more light to enter, heightening visual acuity
  • parasympathetic: dampens the acute stress response for relaxation and normal physiological functions like digestion
    
    • deescalates body from heightened sympathetic state
      
      • lowering heart rate, constricting pupils
      • rest and digest

Question 686

mobilization of autonomic sympathetic nervous system responses

Answer 686

By epinephrine (adrenaline) and norepinephrine produced by adrenal medulla and some sympathetic neurons

Question 687

Ganglia are

Sympathetic neuron intermediates that signal to target organs

preganglionic and postganglionic neurons

Which use acetylcholine neurotransmitter?

Answer 687

Ganglia are synaptic relay statins between neurons

Preganglionic neuron synapses at a peripheral ganglion on the postganglionic neuron which then synapses and acts on target organ

• in parasympathetic NS, preganglionic neurons are long; synapse on ganglia near or on target organs
  
  • both pre and postganglionic neurons use neurotransmitter acetylcholine
• in sympathetic system, preganglionic neurons much shorter and synapse on sympathetic trunk- chain of ganglia near spinal cord extending from base of skull to coccyx
  
  • use acetylcholine
• Sympathetic postganglionic neurons are longer and extend to target organ
  
  • don’t use acetylcholine, instead use norepinephrine

Question 688

Enteric nervous system (peripheral)

Answer 688

Highly complex and semi-autonomous, regulates digestive function

• so complex can be referred to as body’s “second brain”

Question 689

Nervous system function summary

Answer 689

1. Environmental stimuli detected by sensory receptors in bodys periphery
2. Transduced into electrochemical signals and transmitted via afferent fibers (SAME)
   * carry info to central NS
3. Info is processed and translated into sensory perceptions by cerebrum

Question 690

Where 5 senses are processed

Answer 690

Distinct regions of cerebrum for 5 senses

Touch (somatosensation): goes through thalamus, processed in parietal lobe at primary sensory cortex, located on postcentral gyrus (posterior to fold on the brain = central sulcus)

Sight: Signals begin in thalamus and superior colliculus before being processed in occipital lobe before going to primary visual cortex

Sound: first modulated at inferior colliculus before going to thalamus and then primary auditory cortex in temporal lobe

Taste (gustatory pathway): passes through thalamus before ending in gustatory cortex

Question 691

Motor control pathway (important structures in brain, follow signal)

Signals are modulated by ____ before going down spinal cord

What stimulates muscle contraction?

Coordination is heavily dependent on…

Answer 691

Initiated in premotor cortex, executed by primary motor cortex located on the frontal lobe at structure called precentral gyrus (anterior to postcentral gyrus) bordering central sulcus (fold)

• Electrochemical signals generated in primary motor cortex are modulated by:
  
  • cerebellum and basal ganglia, substantia nigra
    
    • coordinates contraction of different muscle groups to unify movement
  • then proceeds down spinal cord to efferent neurons which terminate at a neuromuscular junction
    
    • ​releases acetylcholine on muscle cell, stimulating contraction

**Coordination is heavily dependent on dopamine, the prominent nerve transmitter in the brain

• dopamine disregulation implicated in Parkinson’s

Question 692

Efferent fibers synapse acetylcholine on…

Answer 692

Muscle cells, including smooth and cardiac muscle of internal organs

Question 693

Important neurotransmitters

Answer 693

Acetylcholine- muscle contraction

Norepinephrine-

Dopamine-

Glutamate- amino acid, primary excitatory nerve transmitter

• responsible for neuron depolarization and elicitation of action potentials

GABA: most prominent inhibitory neurotransmitter

• hyperpolarizes neurons, reducing likelihood of firing

Question 694

Neuron structure

Answer 694

Rapid relay of signal; non-dividing highly specialized and electrically excitable cell

• require a lot of support and maintanence - Glial cells
  
  • ​neurons very demanding metabollically, require constant glucose influx by astrocytes (subtype of glial cells)
• Signal input - dendrites
• Signal output- terminal

Soma- cell body; contains nucleus and all cellular organelles

• Between soma and terminal is the axon, which relays signals

Dendrites face a synaptic cleft (small gap b/w two neurons) between them and terminal end

Question 695

Blood-brain barrier

Answer 695

astrocytes: Glial cell which transforms nutrients for neurons with help of epithelial cells and pericytes (surround/support epithelial cells)

• form blood-brain barrier: links neurons and CNS to blood supply

Blood brain barrier is selectively permeable to specific substances, helps maintain stable environment for neurons

Question 696

Glial cells and subtypes

Answer 696

Glial cells provide nutrients, structure, insulation, and defense from pathogens - many subtypes with specialized functions:

• astrocytes: transform nutrients with epithelial cells and pericytes (surround/support epithelial cells)
  
  • form blood-brain barrier: links neurons and CNS to blood supply
  • • ***astrocytes also function as constant, insulin independent active transport of glucose from blood stream to neurons
• satellite cells: nutrient support and protection
• ependymal cells: secretes cerebral spinal fluid

Question 697

Insulation of neurons (myelination)

What provides myelin?

Function of myelination

Answer 697

Insulation provided by oligodendrocytes in CNS and Schwann cells in peripheral NS

• wraps axon in a sheet of a white, fatty substance called myelin
  
  • ​leaves small gaps called nodes of Ranvier

Not all nerves myelinated, but serves purpose of preventing cross-talking b/w axons and speeds of signal transmission

• action potential travels from one unmyelinated gap to the next–> jumping down axon (saltatory conduction)

Question 698

Microglia

Answer 698

First line of defense for central NS

• function like macrophages
• also remove waste in damaged cells, prune some neurons, and eat away extracellular protein deposits

Question 699

Cerebrospinal fluid

Answer 699

Bathes/buffers cells of central nervouse system

• fluid is secreted and circulated by ependymal cells (type of glial cells)

Constant stable chemical environment and physically cushions the CNS

Question 700

Signal Transmission (neurons)

Answer 700

Terminal end of one neuron releases neurotransmitters across synaptic cleft which bind to receptors on dendrites of another neuron allowing influx of specific ions

• causes a change in membrane potential = graded potential; the more neurotransmitters that bind, the more graded potentials created
  
  • graded potentials can travel along the dendrites and soma to the axon hillock, next to axon
    
    • axon hillock is next to voltage-gated sodium channels

If enough graded potentials add up to reach threshold potential (-55mV), action potential is generated and travels down axon

• once action potential reaches terminal, causes calcium channels to open up; influx of calcium creates signaling cascade which leads to exocytosis of neurotransmitters

Question 701

Membrane Potential

Answer 701

Membrane of cells is nonpolar and impervious to ions with exceptions like Na+/K+ ATPase transporter

• ability to regulate entry/exit of specific ions creates membrane potential
  
  • difference in electric potential on each side of membrane; **difference in distribution of charged particles b/w two locations
    
    • measured in volts

More positively charged cells on outside than inside = negative membrane potential

• know this:**inside of cell is rich in negative aminos and K+, outside of cell is rich in Ca²⁺, Na⁺, and Cl-
  
  • overall negative membrane potential of -70 mV

Question 702

Na+K+ ATPase

Answer 702

Enzyme that hydrolyzed ATP to push 3 Na+ ions out of cell for 2 K+ ions

• constitutively expressed in all cells and is always active, accounts for much of cells hydrolyzed ATP
  
  • gives cell resting membrane potential of -70 mV

Question 703

Depolarization of membrane potential

Overshoot of membrane potential

Repolarization

Hyperpolarization

Answer 703

Depolarization: membrane potential becomes less negative and approaches zero

Overshoot: membrane potential becomes positive

Repolarization: returning to the resting membrane potential after the neuron has depolarized (-70 mV)

Hyperpolarization: membrane potential becomes more negative than resting membrane potential -70 mV

Question 704

Voltage gated channel

Answer 704

Usually for Na+

Opens/closes in response to change in membrane potential

Question 705

Graded potentials (different types)

Answer 705

Dendrites contain specific receptors for different neurotransmitters; when a neurotransmitter binds, it allows an ion to flow inside which changes the membrane potential of the cell = graded potential

• most graded potentials are excitatory:
  
  • Excitatory Postsynaptic Potentials (EPSPs): raise membrane potential, making it more positive
  • Inhibitory Postsynaptic Potentials (IPSPs): make membrane more negative =hyperpolarization

Spatial and temporal summation: potentials add up if located close to each other or happen in short time span

Question 706

What happens when threshold potential of a neuron is reached?

Answer 706

Once graded channels add up to threshold potential (-55 mV), voltaged gated sodium channels open up and, like a flood, sodium rushes into cell down its concentration gradient and electrical gradient

• causes membrane potential to increase even further opening up neighboring sodium channels
• **this causes chain reaction, as there are sodium channels all along the axon

Action potential: cascade of depolarization down the axon

Question 707

Repolarization of neuron after action potential fires

Answer 707

Voltage gated potassium channels open up, closing voltage gated sodium channels at abot +35 mV

• loss of cations quickly makes membrane potential negative again, overshooting and causing hyperpolarization

Potassium channels close and **Na+ K+ ATPase brings membrane potential and concentration gradient back to resting

Question 708

Refractory period of neurons (2 types)

Answer 708

Once voltage gated sodium channels close at depolarization peak (~ +40 mV), cannot open again for a certain period of time: absolute refractory period

• new action potential won’t initiate
• serves as a safety check, prevents signal from traveling backwards

Relative refractory period: Na+ channels are able to open again, but the membrane is still hyperpolarized; possible but difficult to generate action potential

Question 709

What happens when action potential reaches terminal end of neuron?

Answer 709

Instead of sodium channels, terminal end of axon has voltage gated calcium channels

• open in response to depolarization/action potential
  
  • opening creates an influx of calcium which causes chemical signaling cascade resulting in exocytosis of neurotransmitters from vesicles into synaptic cleft of next neuron
    
    • vesicles: dedicated storage structures that fuse w/ plasma membrane of terminal

Question 710

What happens to neuroteransmitters after binding to neuron receptor?

Answer 710

Either undergo degradation or reuptake

• degradation: hydrolytic enzymes break neurotransmitter apart
  
  • ex. acteylcholinesterase: catalyzes breakdown of ester linkage of acetylcholine
    
    • strong/immediate effects
• reuptake: neurotransmitters moved out of synaptic cleft by presynaptic neurons or by astrocytes
  
  • _​_various transport proteins in membrane of presynaptic neuron
  • for monoamines (norepinephrine, dopamine, serotonin), reuptake is followed by breakdown by monomine oxidases

Question 711

Regulation of neurotransmission by exogenous chemicals (from outside the body)

Answer 711

Selective Serotonin Reuptake Inhibitors (SSRIs): treatment of depression

Monoamine Oxidase Inhibitors (MAOIs): anti-tuberculosis, anti-depressant

Question 712

Electrical neuron synapse

Answer 712

Sending and receiving neurons are closer together, linked by gap junctions

• allows for direct diffusion of neurons, membrane potential of one neuron can immediately influence that of the other
  
  • * speeds up signal transmission but can’t amplify/modulate the signals

Question 713

How do sensory neurons get triggered?

3 types of receptors

Answer 713

External stimuli has to trigger a graded potential;

1. Thermoreceptor: heat

2. Baroreceptor: pressure

3. Photoreceptor: light

Question 714

Membrane capacitance

Answer 714

Capacitance: how much charge is on both sides of an insulator and thickness of insulator

• insulator is cell membrane
• Charging/discharging membrane requires work, higher the membrane capacitance the more difficult it is to change membrane portential
  
  • neuron harder to depolarize (larger neurons)

Larger neurons have more area to store charge along membrane and therefore have higher membrane capacitance = harder to depolarize

Question 715

Membrane resistance and Cytoplasmic resistance in neurons

Answer 715

Membrane resistance: ability of membrane to keep charges separate

• high membrane resistance = effective action potential transmission
  
  • low membrane resistance can cause leakage of ions

Cytoplasmic resistance: how much the cytoplasm itself impedes the flow of ions

• higher the cytoplasmic resistance, slower the neuron conduction
• **larger the neuron, lower the cytoplasmic resistance

Question 716

Small vs. large neurons

Answer 716

Capacitance: the ability of a system to store an electric charge.

Question 717

How signals travel at fast speeds across long neurons

Answer 717

Membrane resistance, membrane capacitance, and cytosolic resistance will determine conduction speed

myelination: drastically decreases membrane capacitance and increases membrane resistance

• wrapping axon in thick lipid layer; insulating large portions of the axon
  
  • prevents efflux (outflow) of ions (by increasing membrane resistance)

Decreases capacitance: thick layer between cytoplasm and extracellular fluid

**Depolarization decays along these portions, which is why unmyelinated Nodes of Ranvier are necessary to replenish it

Question 718

Nodes of Ranvier

Answer 718

Intermittent, short unmyelinated regions of axon; all usual players are highly abundant (sodium/potassium channels, Na+K+ ATPase)

• depolarization decays slightly in myelinated regions
  
  • when going through Nodes of Ranvier, voltage gated sodium channels open and depolarization is replenished to full intensity

Question 719

Failing to maintain myelination of axons

Answer 719

Hallmark of debilitating neurological diseases

• multiple sclerosis

Question 720

Nernst equation

Question 721

Retina

Cones and Rods

Answer 721

Eye: detect visual stimuli (light) –> action potentials –> brain

Retina: turns certain wavelengths of light into action potentials, located at the back of the eye

• contains millions of photoreceptors (cones and rods)
  
  • cones responsible for perceiving color and fine detail
    
    • 3 diff types for different wavelengths: short, medium, long wavelength
      
      • short: perceives blue, 420 nm
      • medium: perceives green, 530 nm
      • long: perceives red, 560 nm

Cones are centralized in the fovea centralis of the retina, a small pit that only contains cones

• also in the macula, central region around the fovea

Rods don’t sense color: sensitive to visual input, don’t pick up on detail well, responsible for night vision; black and white

• contain rhodopsin compound, pigment that doubles as photoreceptor proteins - sensitive to light

Many more rods than cones, distributed away from center of retina - peripheral vision best for seeing dimly-lit objects at night

C for cones = color

R for rods = rhodopsin, black and white

Question 722

Lens and cornea

Cilliary muscle and cilliary body

Anterior and posterior chamber

Answer 722

Eye converges light on retina to display a clear image

Lens and cornea located at the front of the eye

• cornea: very first thing light passes through to enter the eye
  
  • used for protection and focusing light
• lens: finishes focusing light
  
  • can change shape to help eye focus on objects at diff distances

Cilliary muscle apart of larger cilliary body, used to adjust lens via suspensory ligaments

• Anterior chamber- smaller, front facing area
  
  • contains aqueous humor fluid
• Posterior chamber- larger space towards back of eye
  
  • contains vitreous humor fluid

Question 723

Iris, pupil

Answer 723

iris: colored part of eye with hole in its center = pupil

• pupil lets light into eye, iris is sun shield

Iris is connected to two muscles to help deal with varying levels of light

• dilator pupillae: increases pupil size (pulls iris back); allows more light (happens in the dark)
• constrictor pupillae: decreases pupil size (extending iris), allows less light

Sympathetic NS kicks in –> fight or flight –> pupils dilate

Parasympathetic NS –> rest and digest –> constrict

Question 724

Choroid and sclera

Answer 724

Choroid= middle layer, vascular tissue that supplies retina with blood and absorbs excess light

• forms a continuous layer with the iris

Sclera= outermost layer, continuous with the cornea and accounts for white color of eye

Question 725

Steps between light ray hitting retina and action potential being sent through optic nerve to brain

Bipolar cells, ganglion cells, horizontal cells

Answer 725

1. Cones and rods don’t directly connect to optic nerve; instead, synapse onto neurons known as bipolar cells- called bipolar due to shape

• bipolar cells accept info from multiple cones/rods
• Horizontal cells: in between photoreceptors and bipolar cells; inhibit photoreceptors helping eye to edjust to high light

2. Bipolar cells synapse with ganglion cells, components of the optic nerve
   * mediated by amacrine cells

Question 726

Visual fields and optic nerve

Answer 726

Two visual fields, one for seeing the left and right sides

Each retina field is also divided into two halves, with the left side of the retina corresponding to the right side of the field and vice versa

• ** a light ray to your left will bounce off the right side of retina in both eyes

Optic nerve has four components, one for each half of each retina

• Two optic nerve components cross at optic chiasm (innermost halves of both eyes) = nasal halves (closest to the nose)
  
  • cross over and lead to opposite sides of brain

Input on the outermost halves stay on the same side of brain

**input from the left facing halves of both eyes (right visual field) gets processed on the left hemisphere of brain, input on right facing halves (left visual field) gets processed on the right

Question 727

Optic tract, temporal and spatial resolution

Answer 727

Optic tract: bundles of nerves carrying visual info to each brain hemisphere from the optic nerve

Optic tract runs through the lateral geniculate nucleus, structure in the thalamus that is main relay station for input from retinas

• contain specialized neurons
  
  • magnocellular neurons: large neurons, specialize in detecting motion
    
    • m for motion
    • Temporal resolution: ability to pick up changes
  • parvocellular neurons: small, good at picking up details but not motion
    
    • spatial resolution: ability to see in detail

Visual input further processed in occipital lobe

Question 728

Motion Parallax

feature detection and parallel processing

serial memory processing

Answer 728

Objects that are close to us move further across our visual field than objects that are far from us

• cues for perceiving depth

feature detection: detection of individual stimuli

parallel processing: integrating multiple inputs simultaneously

serial memory processing: systematically giving attention to one thing at a time

• looking for your keys

Question 729

MCAT most often tests vision and hearing in detail

Sound

Answer 729

Sound waves are longitudinal waves that, in air, manifest as regularly repeating changes in pressure as air molecules move back and forth

Ear is a funnel that gathers these waves and converts them to neural signals

Question 730

Vestibular sense

Answer 730

Hair cells in inner ear (organ of Corti) help with balance and our orientation in 3D space - swaying motion in endolymph turned to neural signals

• within inner ear, 3 endolymph containing structures called semicircular canals responsible for sensing rotational acceleration
  
  • when the head rotates, endolymph moves and hair cells resist that motion
  • sends signal to the brain

Semicicular canals arranged perpindicularly like XYZ axes

Inner ear also contains vestibule, which senses linear acceleration

• contains utricle: detects horizontal motion
• saccule: detects vertical motion

Question 731

How do we hear?

Answer 731

Cells responsible for converting sound waves to neural signals are hair cells because they have stereocilia (look like hairs) that poke out into fluid called endolymph

• Sound waves cause stereocilia to move in endolymph which opens up ion channels of the hair cells
  
  • allows small positive ions into cell
  • triggers an influx of calcium ions through voltage gated calcium channels which releases neurotransmitters at the other end of the cell

Question 732

Organ of corti

Answer 732

Ear is divided into outer, middle, and inner ear

• hair cells (which pick up sound waves) are located in the inner ear in a structure called organ of Corti = layer cake
  
  • ​organ of corti consists of basilar membrane on bottom, hair cells in endolympth in the middle, and tectorial membrane above

Sound waves enter ear and cause hair cells to vibrate in endolymph, release neurotransmitters that trigger nerve signals to the brain

Question 733

Outer Ear

Answer 733

Auricle: cartilaginous external ear above the ear lobe

• funnel incoming sound waves into auditory canal which leads to ear drum
  
  • ​ear drum (tympanic membrane): vibrates in response to sound waves
    
    • high frequency waves = high freq vibrations
      *

Question 734

Middle ear

Answer 734

Contains ossicles: 3 tiny bones that fit together to amplify the vibrations (by as much as 10x) of the tympanic membrane (ear drum)

• malleus connected to ear drum
• sends vibrations to the incus
• incus connects to the stapes

Stapes connects to the oval window, boundary between middle ear and inner ear - sends amplified vibrations to inner ear

Middle ear also contains a connection to the nasal cavity: Eustachian tube: valve that equalizes the pressure between middle ear and environment (ears popping)

Question 735

Inner ear

Answer 735

Bony labyrinth: basic framework of inner ear

Area between bony labyrinth and membranous labyrinth contains perilymph, fluid similar to endolymph

• membranous labyrinth: within bony labyrinth, makes up sub-structures of inner ear
  
  • contains endolymph

Cochlea: Structure responsible for hearing; spiral shaped and divided into three layers called scalae

• middle layer contains organ of corti
  
  • ​hair cells protrude from basilar membrane, bathed in endolymph
    
    • layer below is filled with perilymph, vibrates in response to sound which are transferred to basilar membrane

Question 736

Basilar membrane

How aging affects hearing?

Answer 736

Receives vibrations from organ of Corti

• Place theory: thickness of basilar membrane isn’t constant
  
  • different thicknesses respond to different frequencies
• thickest in response to high frequency vibrations at its base, next to oval window
  
  • narrowest at apex
• Allows brain to infer the pitch of a sound based on which hair cells send signals

As we age, damage to hair cells and stiffening of basilar membrane contribute to age-related hearing loss

Question 737

Ear divisions

Answer 737

Outer ear: gathers sound waves

Middle ear: amplifies

Inner ear: sound detection, organ of Corti

Question 738

auditory processing from organ of Corti

Left hemisphere is used for?

Right hemisphere?

Answer 738

Nerve signals generated by hair cells are transmitted through vestibulocochlear (auditory) nerve

• passed through medial geniculate nucleus in the thalamus on the way to auditory cortex in the temporal lobe

Left hemisphere- speech

Right hemisphere- background noise, music

Question 739

Touch

two point threshold

physiological zero

Answer 739

Somatosensation: touch, pain, temperature, pressure, stretching

Nerves in body aren’t distributed evenly, some areas are more dense

• tips of fingers more sensitive, skin on back of head insensitive

two point threshold: minimum distance for distinguishing two point stimuli

• the denser the nerve distribution, the smaller the two point threshold

Physiological Zero: reference point of our skin, call temp hot or cold based on this

• skin is usually cooler than core body temp

Question 740

Gate theory of pain

Answer 740

Body can turn pain signals on or off in the spinal cord

• Intensely painful stimulus can override less painful one
• different people have different pain thresholds

Question 741

Differences between taste and smell receptors

Answer 741

Both taste and smell use chemoreceptors

• Olfactory (smell) receptors respond to huge range of stimuli dissolved in the air
  
  • processed in olfactory bulb then passed to olfactory tract
    
    • then processed by other parts including limbic system (emotion)
• Gustatory (taste) receptors pick up smaller range of tastes of substances dissolved in fluids
  
  • processed in thalamus then sent to gustatory cortex

Question 742

Sensation vs. Perception

Answer 742

Sensation doesn’t equal perception

sensation: real, physical objects information is detected by our body (objective)

perception: our brains personal experience of sensory information (subjective)

Question 743

Sensory receptors - communicate four properties to central NS

Answer 743

Specialized dendrites of sensory neurons that respond to various physical stimuli - action potentials sent to CNS

• bundled together into ganglia (cluster of nerve cells)

4 properties communicated to CNS:

1. ​location: where stimulus is coming from
2. modality: type of stimulus
3. intensity: how strong the stimulus is
4. duration: how long a stimulus lasts

Question 744

Types of sensory receptors

Answer 744

Exteroreceptors: respond to stimuli from outside world

• 5 senses

Interoreceptors: respond to internal stimuli

• can sense internal pain
• dehydration/overhydration
  
  • baroreceptors: detect pressure inside the body, like walls of blood vessels
    
    • blood pressure linked to blood volume and hydration
  • osmoreceptors: detect concentration of solutes in blood
    
    • triggers responses when blood becomes too dilute or concentrations
  • propioreceptors: found in and around muscles, tendons, joints
    
    • responsible for giving kinesthetic sense of relative position of the parts of our body in space

Question 745

Receptors responsible for taste and smell?

Answer 745

Olfactory receptors: sense of smell

• respond to volatile chemicals (chemicals in air)
• sensitive to near limitless range of chemicals

Gustatory receptors: sense of taste

• respond to chemicals dissolved in saliva
• more limited

Both response to chemical stimuli

Question 746

Receptors responsible for vision and hearing?

Answer 746

Photoreceptors: responsible for vision reception

• respond to specific wavelengths of light

Hair cells: responsible for sound reception

• convert pressure signals from sound waves into action potentials
• also use pressure to respond to rotational acceleration (balance)
  
  • semicircular canals
  • hair cells in crista ampullaris send rotational info to NS

Question 747

Receptors responsible for touch

Answer 747

Mechanoreceptors: respond to mechanical stimuli

• different types detect different stimuli (don’t need to memorize)
  
  • tactile corpuscles: detect light touch
  • merkel nerve endings: respond to sustained pressure
  • Ruffini endings: sense deep pressure beneath surface of skin
  • Pacinian corpsucles: detect high frequency vibrations

Question 748

Receptors that detect pain

Answer 748

Nocireceptors detect pain, mechanical, chemical and thermal stimuli

Question 749

Proximal and distal stimuli

Answer 749

Proximal stimulus: what the sensory receptor picks up on

Distal stimulus: environmental source of signals

Question 750

Absolute threshold

Threshold of conscious preception

Answer 750

Absolute threshold: Level of intensity that a stimulus must have in order to be picked up by sensory neurons

• if a stimulus doesn’t hit threshold, not registered by our bodies
• experimental design minimizes any other influences

Threshold of conscious preception: threshold a stimulus must cross in order for our bodies to consciously perceive it

• other factors can distract even if stimuli crosses absolute threshold

Question 751

Just Noticeable Difference (of stimuli)

Weber’s Law

**know this

Answer 751

Smallest change in magnitude of a stimulus that we can perceive as being different

• psychophysical discrimination testing

Weber’s Law: for any given sensory input, the just-noticeable difference will be a constant proportion of the original output

• ex. can detect 10% increase in weight = 1 to 1.1 lbs, 10 to 11 lbs; 100 to 110 lbs
  
  • can’t detect 100 to 105
• Breaks down at extremes (too strong, too faint)

Question 752

Signal Detection theory

Answer 752

Want to maximize hits and correct rejections, minimize misses and false alarms

Signal detection can vary across people and psychological states

Relevant to diagnosing medical conditions

Question 753

Sensory Adaptation

Answer 753

Getting used to stimuli, blocking out other stimuli

• partly occurs in brain, primarily in sensory receptors

Tonic receptors: receptors that are slow to adapt to stimuli

• respond as long as the stimuli is present
  
  • stretching, pain

Phasic receptors: send a burst of action potentials, then stop (fast adaptation)

• hair follicles

Question 754

Two types of processing for perception

Answer 754

Bottom up processing: brain starts with individual pieces of sensory info and assembles them into a coherent whole

Top down processing: brain decides what its looking for ahead of of time and assembles individual pieces in a way that supports the picture

Both types coexist for all of our senses

• hearing a song then trying to recognize what the name is

Question 755

Gestalt Principles of Grouping (principle of proximity, similarity, and good continuation, closure, symmetry)

Law of Pragnaz

Answer 755

Principle of proximity: we perceive objects or shapes close together as forming groups

Principle of similarity: objects similar in some way will be perceived in a group

Principle of good continuation: if multiple objects overlap, perceived as a continuation of few objects

** principles don’t apply in isolation

Principle of closure: We infer the presence of complete shapes even when they’re incomplete

Principle of symmetry: symmetrical objects more likely to be perceived as parts of a whole than asymmetric

Law of Pragnaz- overall, objects perceived in the simplest most meaningful ways

Question 756

Depth

Answer 756

• Depth- ability to perceive a third spatial dimension
  
  • near vs. far in addition to up/down, left/right
  • perceived using binocular eye clues (both eyes)

Question 757

Endocrine system vs exocrine glands?

Merocrine?

Apocrine?

Holocrine?

Answer 757

-crine = secrete

Endocrine system is a collection of organs and tissues whose job is to produce/release hormones at the right times DIRECTLY into circulation

• exocrine glands: secrete their products through a duct
  
  • ex. salivary glands, liver and pancreas, sebaceous glands (secrete skin oils)
  • ACT LOCALLY, can’t affect organs or tissues at a distance

Merocrine: release products through exocytosis

• sweat glands

Apocrine: releases products by membrane budding

Holocrine: release products via membrane rupture and cell lyse

Question 758

Endocrine glands release…

Most important endocrine glands

Answer 758

Endocrine glands release hormones (signaling molecules) into bloodstream to act on target tissues from a distance

• certain hormones can also function as neurotransmitters dpending on HOW its secreted
  
  • norepinephrine, oxytocin, antidiuretic hormone

Hypothalamus, pituitary gland, thyroid, adrenal gland, pancreas

Question 759

Organs with endocrine and exocrine function

Answer 759

Pancreas:

• has pancreatic islets with endocrine functions
  
  • releases key hormones like insulin and glucagon
• acinar cells with exocrine functions
  
  • release digestive enzymes into GI tract through pancreatic duct

Question 760

Tropic vs. Non tropic hormones

Answer 760

Tropic hormones: target other endocrine glands, usually stimulate release of another endocrine hormone

• most are produced and secreted by hypothalamus and anterior pituitary gland
• give more opportunities for processes to be regulated (more important implications)

Non-tropic (DIRECT) hormones: act on non-endocrine tissues

• cause direct physiological effect

Question 761

Some common uses for synthetic hormones

Answer 761

Synthetic estrogens and progestrogens, oral contraceptives

Thyroid hormone thyroxine to treat hypothyroidism

Steroid hormones for autoimmune diseases

Injectable insulin for diabetes

ACE inhibitors lower blood pressure by inhibiting angiotensin converting enzyme

Question 762

3 major classes of hormones

Answer 762

Peptide hormones, steroid hormones, amino acid derivatives

Question 763

Peptide hormones

vs.

Steroid hormones

Answer 763

Essentially peptides varying in amino acid number/length of aminos

• HYDROPHILIC; diffuse freely into bloodstream, no need for blood transport proteins
  
  • However, CAN’T diffuse through cell membranes, must bind to extracellular receptors
    
    • intracellular second messagers then elecit desired effect
      
      • ex. cAMP, Ca2+, IP₃
• Rapid, short time changes

Steroid hormones are derived from the lipid cholesterol and contain its characteristic 4 ring structure

• HYDROPHOBIC; ride carrier proteins in the blood stream
  
  • carrier protein examples: sex hormone binding globulin, albumin
    
    • easily diffuse through cell membranes and bind with receptors (usually nuclear receptors that function as transcription factors)
    • Triggers conformational shift that ACTIVATES receptor –> binds to DNA and promotes/represses transcription
      
      • effects take a while, last longer than peptide homrones

Question 764

Where are steroid hormones produced?

How are peptide hormones produced

Answer 764

Steroid hormones synthesized from cholesterol in the smooth ER and diffuse directly through cell membrane into bloodstream

Peptide hormones produced by transcription of relevant mRNA, translation into polypeptide –> preprohormone

• preprohormone is secreted into rough ER and modified into prohormone –> golgi apparatus
  
  • in golgi, cleaved by peptidases and sometimes modified by glycosylation into peptide hormones
  • leave golgi in vesicles

Question 765

Amino acid derived hormones

Answer 765

Some behave like peptide hormones, some behave like steroids

Small molecules derived from a SINGLE amino acid

• ex. T3 and T4 hormones derived from tyrosine - both hydrophobic, behave like steroid hormones w/ long lasting effects

Others like epinephrine and norepinephrine are water-soluble and act like peptide hormones - powerful but short lived

Some are amphipathic

Question 766

How does endocrine system know when to release hormones?

What happens when youre stressed?

Answer 766

Neuroendocrine integration: nervouse system senses changes in environmental conditions and communicates to endocrine system

• hypothalamus in the brain responds to nervous system input and secretes tropic hormones that stimulate the production of other hormones from the pituitary gland
  
  • _​_pituitary hormones act on organs throughout the body

1. Nervous system notifies hypothalamus which releases the tropic hormone corticotropin-releasing hormone (CRH) which
   
   1. binds to anterior pituitary gland which then releases adrenocorticotropic hormone (ACTH)
2. ACTH acts on adrenal cortex which secretes cortisol into circulation

Cortisol- steroid hormone released during periods of long term stress

Question 767

Cortisol

Pathway that leads to cortisol release is called…

Regulation of this pathway by…

Answer 767

Steroid hormone released during periods of long term stress

Increases metabolism of fats, proteins, and sugars

• if chronically elevated, can lead to weight gain, immune suppression, and increased risk of diabetes

Hypothalamic-Pituitary-Adrenal

1. Nervous system notifies hypothalamus which releases the tropic hormone corticotropin-releasing hormone (CRH) which
2. binds to anterior pituitary gland which then releases adrenocorticotropic hormone (ACTH)
3. ACTH acts on adrenal cortex which secretes cortisol into circulation

Cortisol regulates pathway by negative feedback by inhibiting CRH and ACTH

However, hypothalamus and pituitary gland gradually become less sensitive to it if stress continues, cortisol levels can elevate

Question 768

Almost all feedback pathways in the endocrine system are…

Answer 768

Negative feedback loops - downstream product feeds back to inhibit earlier point in pathway

• prevent physiological parameters like blood pressure and blood glucose from getting too high or low

Question 769

Positive feedback in the endocrine system

Answer 769

Much less common than negative feedback

• Oxytocin pathway:

1. Oxytocin is peptide hormone secreted by the posterior pituitary
   
   1. stimulates uterine contractions during labor
2. First uterine contractions stimulate the release of more oxytocin
   
   1. induces stronger uterine contractions
3. Amplifies until baby is born

Question 770

Gonads vs. Genitalia

Male reproductive external anatomy

Answer 770

Gonads: where gametes are made

• in males, gametes are sperm and gonads are testes

Genitalia: internal and external reproductive organs

• in males, external genitalia are penis and scrotum (ballsack)

Testes: site of spermatogenesis: production and maturation of male gametes

• secrete androgens (sex hormones, testosterone)
• functions best at a few degrees below body temperature

Testicular thermoregulation: position of the scrotum is controlled by two muscles

• the cremaster: contracts to draw testes closer to the body
• and dartos muscles: contracts to wrinkle the scrotal skin

Question 771

Within the testes ____ takes places

Answer 771

Spermatogenesis takes place in a series of coiled tubes = seminiferous tubules, separated by barriers called septa

• Production of spermatazoa (sperm) from germ cell precursors is facilitated by Sertoli cells, which make up epithelium of seminiferous tubules

Next to seminiferous tubules are endocrine cells called Leydig cells, secrete androgens such as testosterone

1. immature spermatazoa goes from tubules to the epididymis **used for storage and maturation of sperm
   
   1. nonmotile in epididymis, gain motility over period of 2-3 months
      
      1. either ejactulates or gets reabsorbed

Question 772

When ejaculation occurs

Answer 772

Sperm travels from epididymis (storage and maturation) to the vas deferens which connects to ejactulatory ducts, formed by fusion of vas deferens with seminal vesicles

Seminal vesicles: generate majority of semen liquid component; nutrients like fructose, vitamins, enzymes

Ejaculatory ducts travel through prostate gland and then join with the urethra

• Cowper’s gland (bulbourethral): produce preejaculate which lubricates the urethra, neutralizes acidic urine

SEVE UP (picture)

Question 773

Spermatazoa vs. Semen

What is Azoospermia?

Answer 773

Spermatazoa: haploid gametes that fertilize eggs

Semen: alkaline nutrient filled liquid

• carries sperm through reproductive tract
• **Basic as a buffer from acidic environment of female reproductive tract, protecting DNA from degradation

Azoospermia: semen containing no sperm

Question 774

Internal female genatalia

External female genatalia

Answer 774

Internal: Ovaries, fallopian tubes, uterus, cervix, vagina

External genatalia collectively known as vulva: labia majora, labia minora, clitoris, vaginal orifice, urethral opening

• labia minora: helps protect urethral opening from irritation/infection
• clitoris: sex organ,

Question 775

Oogenesis is

Ovaries two functions:

Answer 775

Production of female gametes, occurs in the ovaries (female gonads)

• results in the production of mature ova “eggs”
• contain many follicles, each of which houses immature egg called oocytes
  
  • ​all PRIMARY oocytes are produced before birth, ~400,000 follicles at start of puberty

Ovaries also have endocrine function, producing estrogen and progesterone

Question 776

Ovulation and ovum journey

Answer 776

Ovulation: during each menstrual cycle, one follicle releases secondary oocyte into the peritoneal cavity

• ovum is swept up into fallopian tubes by cilia, transported to uterus by cilia and peristaltic contractions of smooth muscle

If an ovum is fertilized by sperm in the fallopian tubes, then implants in the wall of uterus where fetus develops during pregnancy

Question 777

3 layers of the uterus

Answer 777

1. Endometrium: innermost layer, mucous membrane of epithelial cells that thickens and thins over course of menstrual cycle in anticipation of implantation

2. Myometrium: smooth muscle

3. Perimetrium: outer layer

Question 778

Cervix and vagina

Answer 778

• Cervix: Cylindrical structure that connects the uterus to the uterine cavity
  
  • sperm must travel through cervical canal and uterus for fertilization
  • connects to vagina
• Vagina: elastic walls allow vaginal canal to stretch and accomodate a fetus during childbirth
  
  • also home to a rich population of bacteria, maintaining healthy microbiota is important aspect of reproductive health

Question 779

Spermatogenesis

Answer 779

Male gametogenesis which produces spermatazoa

1. Begins with spermatogonial stem cells which can follow one of two paths:
   
   1. divide to form more stem cells
   2. differentiate into spermatogonia
2. Spermatogonia (diploid) undergo spermatogenesis, start by mitosis
   
   1. Form two spermatocytes
3. Then undergo meiosis I
   
   1. _​_2 haploid, sister chromatids (two copies of each chromosome)
4. _​​_Secondary spermatocytes undergo meiosis II to form 4 haploid spermatids with one copy of each chromosome

Spermatids undergo spermiogenesis

• formation of tail
• loss of excess cytoplasm
• formation of acrosomal cap- enzymes required for fertilization
• still not motile - gain this in epididymis

Question 780

Mature sperm cell has 3 parts:

Answer 780

1. Head: cells nucleus, surrounded acrosomal cap
2. Midpiece: abundant mitochondria, provide energy
3. Tail: provides motility

Question 781

Steps of oogenesis

Answer 781

1. Oogonia formed by primordial germ cells
   * just like in spermatogenesis, differentiate into primary oocytes

2. Undergoes meiosis I, EXCEPT halted in prophase I until puberty

• beginning at puberty, small number of oocytes resume oogenesis
  3. Diploid cell divides into one haploid (1n) secondary oocyte and one polar body (receives much less cytoplasm, dies)
• secondary oocyte is released from ovarian follicle each month
  4. IF FERTILIZED, resumes meiosis II, creating a zygote and a second polar body

Question 782

Hypothalamus functions

Answer 782

Almond sized region of the forebrain, bridge between nervous and endocrine systems

• controls autonomic activities like body temp, metabolism, fatigue, sleep

Also oversees activity of the pituitary gland, which regulates other endocrine glands

Question 783

Pituitary gland consists of:

Similarites b/w lobes:

Answer 783

Consists of anterior and posterior glands lobes; both of which receive input from hypothalamus but in different ways

• anterior lobe: receives input via hormonal signals
• posterior lobe: receives input via neuronal signals

Similarities: both secrete peptide horones, both receive hypothalamic input

Question 784

Anterior pituitary gland and the hypophyseal portal system

Answer 784

Receives hormonal input from hypothalamus

• Physically connected to hypothalamus via hypophyseal portal system: system of blood vessels at the base of the brain
  
  • contains extremely permeable endothelial (blood and heart cells) cells
    
    • **allows for exchange of hormones/other small molecules
  • Regulates anterior pituitary hormone production with tropic hormones –> leads to secretion of other tropic hormones

Question 785

Tropic hormone naming patterns

Major hypothalamic tropic hormones

Answer 785

Hypothalamic tropic hormones are “something-releasing hormone”, something referring to next tropic hormone in pathway (usually anterior pituitary hormone)

Anterior pituitary hormones named “something-stimulating hormone”, referring to next and final hormone in pathway

ex. thyrotropin releasing hormone (TRH) tells anterior pituitary to release thyroid stimulating hormone (TSH) which tells thyroid to produce T3 and T4
ex. gonadotropin releasing hormone (GnRH) which tells anterior pituitary to release LH and FSH which play roles in reproduction and growth

• in males LH, stimulates Leydig cells in testes to release testosterone and FSH promotes spermatogenesis
• in females, LH stimulates estrogen production from ovaries, FSH promotes maturation of ovarian follicles

ex. corticotropin-releasing hormone (CRH), releases adrenocorticotropic hormone (ACTH) which travels to adrenal cortex and produces corticosteroids: stress response and circadian rhythms

Question 786

Anterior pituitary hormones (not from hypothalamus activation)

Answer 786

Prolactin: acts on the mammary glands to stimulate milk production

Endorphins: reduce reception of pain

Question 787

Non tropic endocrine hormones - Thyroid

Answer 787

Thyroid is located on the front of the trachea

• secretes T3 and T4 which increase metabolic rate
  
  • Hypothyroidism: slow metabolic rate - weight gain, fatigue
  • Hyperthyroidism: accelerates metabolic rate - weight loss, tachycardia

Thyroid also secretes the hormone calcitonin: reduces calcium concentration in the blood stream

• promotes storage of Ca in bone, increases urinary excretion of calcium
  
  • “toning down” calcium in blood

Question 788

Posterior pituitary gland

two main posterior hormones

Answer 788

Bundle of neuronal axons whose cell bodies originate in hypothalamus

• extension of hypothalamus
  
  • all of hormones released are synthesized in hypothalamus, travel down neuronal axon and are stored in posterior pituitary until signaled by hypothalamas

2 main hormones:

1. Oxytocin: contractions during labor
2. Anti-diuretic hormone (ADH): helps maintain fluid balance in body, released when blood volume gets too low and osmolality (salt conc) is too high; also increases blood pressure

• blocks diuresis (urine production) to help body maintain fluid
  
  • promotes water reabsorption in kidneys

Question 789

Parathyroid Glands

Answer 789

Release parathyroid hormone: opposes effects of calcitonin in order to increase calcium levels in blood

• promotes calcium absorption in the intestines
• reduces calcium storage in bone and calcium excretion in urine

Question 790

Adrenal glands

3 corticosteroids release is stimulated by ____?

Answer 790

Sit on top of the kidneys, two distinct areas (similar structure to kidneys):

1. adrenal cortex: secretes steroid hormones corticosteroids ​
   
   1. Release of corticosteroids is stimulated by adrenocorticotropic hormone (ACTH) from anterior pituitary
   2. ​3 corticosteroids
      
      1. ​glucocortisoids (cortisol): sugar
         
         1. cortisol released in response to stress and low blood glucose, also suppresses inflammation
      2. mineralocorticoids (aldosterone): influence fluid and salt balance
         
         1. aldosterone promotes fluid retention by increasing sodium reuptake
      3. sex hormones (androgens and estrogens): low level production, moreso in sex organs
2. medulla: interior region of each gland surrounded by the cortex
   
   1. produces amino acid derived horones epinephrine and norepinephrine (catecholamines)
      
      1. sympathetic fight or flight
         
         1. epinephrine used in Epi-Pens to treat anaphylaxis

Question 791

Pancreas and 3 cell types

Answer 791

Located posterior to the stomach

Produces hormones important for metabolism, bridge b/w endocrine and digestive systems

• specialized cell types each release diff hormones
  
  • alpha cells: release glucogon in response to low blood sugar
    
    • promoting catabolism via gluconeogenesis and glycogenolysis
  • Beta cells: release insulin, opposes effects of glucagon by promoting glucose uptake in body tissues
  • Delta cells: secretes somatostatin (growth-hormone inhibiting hormone)
    
    • reduces stomach acid secretion and blocks release of other digestive hormones to slow digestion

Question 792

Reproductive organ hormones

Answer 792

Testes and Ovaries

Respond to LH and FSH from anterior pituitary to release testosterone in males and estrogen in women, help develop secondary sex characteristics

Question 793

Secondary Endocrine Organ - Pineal Gland

Answer 793

Small structure near brain stem: secretes melatonin

• regulates sleep cycles and wakefulness
  
  • sold OTC for insomnia

Question 794

Secondary Endocrine structures - the heart’s hormone

Answer 794

Atrial Natriuretic Peptide: produced by muscle cells in the heart, helps regulate fluid balance like aldosterone and anti-diuretic hormone but opposite effect

• released in response to high blood volume
  
  • decreases blood pressure by promoting fluid loss

Question 795

Immune system endocrine organ and function

Answer 795

Thymus- secretes thymosin, hormone that helps T cells develop and mature

Question 796

Digestive endocrine hormones

Answer 796

Gastrin

Secretin

Cholecystokinen (CCK)

Question 797

6 key endocrine (hormonal) processes:

Answer 797

Blood glucose

Blood calcium

Stress

Fluid balance

Metabolic rate

Sexual development

Question 798

Blood glucose regulation

Hormones with effects

Answer 798

Normal blood glucose range : 70 mg/dL to 140 mg/dL

• too little = tissues starved
• too much = glucose not being stored and physiological consequences

Insulin- produced by beta cells in pancreas in response to elevated glucose levels (i.e. after a meal)

• once released, binds to receptors on wide range of target cells mobilizing the cells glucose transporters, lowering conc of glucose in the blood

Glucagon- produced by pancreatic alpha cells when blood glucose levels are too low

• increases glycogenolysis and gluconeogenesis, which liberate glucose and result in high blood sugar

Glucose and insulin also affect protein and lipid metabolism

Cortisol (glucocorticoid released by adrenal cortex): increases blood glucose in fasting state by activating gluconeogenesis and glycogenolysis in the liver

Epinephrine (adrenal medulla): raises blood sugar by stimulating glycogenolysis in liver and muscle cells; fight or flight response

Growth hormone: increases blood glucose under intense physical stress or periods of growth and development

Question 799

Endocrine calcium regulation in the body

hormones

Answer 799

Necessary for proper bone development, muscle contraction, signal transduction

• travels through the bloodstream and body must maintain specific levels

Parathyroid Hormone (PTH): parathyroid gland secretes PTH when calcium levels get too low

• stimulates bone resorpotion*; osteoclasts break down bone and release calcium

Calcitonin (opposes PTH): released by thyroid gland in response to high calcium levels, inhibits osteoclasts

Vitaman D (D2, D3)

• Calcitriol: hormonally active form that regulates calcium homeostasis
  
  • increases serum calcium levels by promoting calcium absorption from GI tract, reducing secretion in urine and activating osteoclasts

Question 800

Endocrine maintenance of fluid levels

Two problematic systems:

Answer 800

Blood volume and omsolality in vascular system

1. Too much fluid raises blood pressure: more pressure, solutes more dilute = lower blood osmolality

2. Too little fluid lowers blood pressure: less fluid available to exert pressure on vessel walls; amount of solute stays constant blood osmolality is high

Question 801

Renin-angiotensin-aldosterone system (RAAS)

Answer 801

Juxtaglomerular cells of kidney sense a decrease in fluid levels and release an enzyme called renin

• Renin cleaves angiotensinogen, inactive protein from the liver
  
  • liberates angiotensin I

Then, in the lungs, angiotensin-converting enzyme (ACE) converts angiotensin I into angiotensin II

• angiotensin II travels to adrenal cortex and simulates aldosterone release, increases fluid retention and blood pressure
  
  • promotes reabsorption of ions in the nephron (kidney)

As blood pressure increases, kidney stops producing renin (negative feedback)

Question 802

RAAS Dysregulation

Answer 802

RAAS can become pathologic when dysregulated

• excess aldosterone can cause dangerous increases in BP

ACE inhibitors: treatment for high BP

Question 803

Maintenance of BP and fluid levels: hormones for low BP

Answer 803

Aldosterone and Antidiuretic hormone (aka vasopressin): fluid retention increases, blood pressure increases (through different mechanisms):

aldosterone: secreted by adrenal cortex in response to low blood pressure

• regulated by Renin-angiotensin-aldosterone system (RAAS)
• promotes Na reabsorption, maintains osmolality

antidiuretic hormone (vasopressin): secreted by posterior pituitary in response to low BP and high plasma osmolality

• increases the permeability of kidneys collecting duct to water
• initially reduces blood osmolality

Question 804

Maintenance of fluid levels: hormone when BP is too high

Opposite of

Answer 804

Atrial Natriuretic Peptide (ANP): produced by cardiomyocytes (muscle cells of the heart); released in response to high blood volume

• opposite of aldosterone and vasopressin (ADH)
  
  • decreases sodium absorption in distal tubule and collecting duct of kidney
• increases filtration rate in glomerulus
• inhibits aldosterone release

Decreases blood pressure by promoting fluid loss

Question 805

Endocrine regulation of stress (short term and long term)

Answer 805

Short-term(acute) stress: fight or flight response

• epinephrine and norepinephrine: catecholamin hormones from amino acid tyrosine; released by adrenal medulla
  
  • released in response to sympathetic NS
  • increase blood glucose, heart and breathing rates, pupil dilation, blood diversion

Long-term(chronic) stress: repeated exposure to stress

• cortisol: increases blood glucose by stimulating gluconeogenesis (opposes insulin)
  
  • suppresses inflammation
  • deleterious long term effects

Question 806

Endocrine regulation of metabolic rate:

2 hormones

Answer 806

Thyroid hormones T3 and T4 released in respond to Thyroid Stimulating Hormone (TSH), which is released by anterior pituitary

T4: four iodine atoms, precursor to T3

T3: 3 iodine atoms

• 3-4 times more potent than T4

Insufficient levels lead to hypothyroidism: fatigue, cold intolerance, weight gain, depressed heart/respiratory rates

hyperthyroidism: weight loss, increased appetite, rapid heart rate

Question 807

Endocrine regulation of sexual development and puberty

LH, testosterone and estrogen

Answer 807

During fetal development, presence of androgen hormones –> development of male/female traits

• then, sex hormones have little effect until hypothalamus-driven surge of hormones called puberty
  
  • ​pulses of gonadotropin-releasing hormone (GnRH) stimulate anterior pituitary to release leutinizing hormone LH and follicle stimulating hormone (FSH)

Females: In response to leutinizing hormone (LH) and FSH, ovaries produce more estrogen and progesterone

• initiate and regulate the menstrual cycle
• promote development of female secondary sex traits (enlarged breasts, widened hips)

Males: LH and FSH act on testes to trigger release of downstream hormones

• LH causes Leydig cells of testes to produce testosterone
  
  • ​Testosterone contributes to male secondary sex traits like facial hair and voice deepening
• FSH affects Sertoli cells, trigger the release of factors for sperm maturation

Question 808

Estrogens and Androgens

What are primary and secondary sex characteristics?

Answer 808

Classes of Hormones; both produced in males and females but at varying levels

• Estrogen: estradiols, progesterone
• Androgen: testosterone

Primary traits: reproductive organs (penis, testes, ovaries)

Secondary traits: changes in fat distribution, hip widening, growth of breast in females; facial hair and deeper voice in males

Question 809

Sex hormones in adulthood

Menopause

Answer 809

Females: estrogen and progesterone regulate menstrual cycle; if pregnancy occurs, levels continue to rise

• at beginning of pregnancy, both produced in corpus luteum (formed by ruptured follicle cells) in the ovaries
  
  • later, taken over by placenta, which also produces Human Chorionic Gonadotropin (hCG)
    
    • ​produced in placenta and maintains corpus luteum during pregancy (detected on pregnancy tests)
• oxytocin in childbirth

Throughout aging, sex hormones produced less but much more abrupt in females

Menopause: typically occurs in 40s or 50s, plunging sex hormone levels and cessation of menstruation

• hot flashes, night sweats

Question 810

Sex hormones in medicine

Answer 810

Hormonal contraceptives, hormone replacement therapy

• synthetic hormones
• prevent pregnancy or mitigate menopause
• polycystic ovary syndrome
• facilitate secondary sex characteristics in transgenders

Question 811

Estrogen is produced by

Answer 811

Ovarian follicle cells, corpus luteum formed from ruptured follicle cells, and placenta

(anterior pituitary forms GnRH which leads to production of estrogen)

Question 812

Menstrual Cycle in females

3 main parts:

Answer 812

Hormonal and physiological changes in reproductive tract

• 28 day interval, beginning in puberty ending in menopause
  1. Ovarian Cycle- 3 phases all in ovary all to release ovum

1. Follicular phase- follicle matures
2. Ovulaton- egg released
3. Luteal phase- after ovum is released, follicle is transformed into corpus luteum
   
   1. if pregnancy doesn’t occur, corpus luteum decays

2. Uterine cycle- uterus preparing for the ovum

1. Menses/menstruation: same time as follicular phase, uterine endometrium thins as tissue buildup in previous cycle is sloughed off
   
   1. typically 3-5 days but variation
2. Proliferative phase: Once menses is complete, uterine endometrium thickens/enriches with blood vessels
3. Secretory phase (during luteal phase): Lining continues to thicken and if ovum is fertilized and implants pregnancy begins

3. Hormone regulation:

At beginning of follicular phase, increase in FSH that induces follicular development; estrogen levels rise to stimulate endometrium development

• Rare estrogen positive feedback on hypothalamus that stimulates brief surge in LH and FSH –> triggers ovulation
  
  • causes ruptured follicle to form corpus luteum

In the luteal phase, corpus luteum secretes high levels of progesterone which help maintain endometrium readiness for implantation

Question 813

How does body know that implantation has occured?

Answer 813

If body didn’t know implantation had occured, embryo would be destroyed during menstruation

In the absence of implantation, negative feedback loops keep menstrual cycle moving forward

• corpus luteum usually responds to LH but progesterone (secreted by luteum) inhibits LH, causing corpus luteum to degrade

If implantation occurs, embryo secretes Human Chorionic Gonadotropin (HCG) which maintains corpus luteum

• continues producing progesterone, maintains uterine endometrium
• then progesterone levels taken over by placenta

Question 814

Oxidation reduction reactions

Answer 814

One atom gains electrons, another atom loses them on (on same side of eqn)

• not just trading out substituents

OIL RIG

All atoms have an oxidation state based on position on periodic table

• losing electrons increases charge, oxidation state increases = oxidized

Reduction- when reduced, oxidation state is lowered (from 0 charge to -2)

• gain of bonds to hydrogen, loss of bonds to EN atoms like oxygen

Oxidation- gaining electrons is being reduced, losing them is being oxidized

• losing bonds to H, gaining bonds to O

Question 815

Oxidizing and Reducing agents

Answer 815

Species that is reduced (loss of charge/gain of electrons) = oxidizing agents

• Often contain Cr, O, or other EN element
  
  • Na₂Cr₂O₇ - sodium dichromate
  • CrO₃ - chromium trioxide
  • PCC
    
    • weak oxidizing agent

Species that is oxidized (gain in charge/loss of electrons) = reducing agent

• NaBH₄ -weak
• LiAlH₄ strong

Usually talking about specific compounds you can add to a mixture to reduce or oxidize another compound

Question 816

Oxidation States

Answer 816

All atoms have different electronegativity and share electrons unequally

• complete in the case of ionic bonds
• partial in polar covalent
• minimal in nonpolary covalent

Assigning oxidation states:

1. Pure elements are 0 - H₂, O₂, F₂, N₂, Na, Fe
2. Monoatomic ions equal to their charge
   
   1. Fe²⁺ = +2, Cl^- = -1
3. Sum of oxidation states is equal to overall charge of compound
4. F is always -1, halogens are -1 unless bonded to more EN halogen, N, or O
5. H is +1 unless bonded to more electropositive element (then its -1)
6. Oxygen is -2 unless its a peroxide (-1)
7. Alkali metals always +1 (like hydrogen), alkaline earth metals always +2

Go through functional groups for larger compounds

**oxidation state of carbon can vary dramatically

Question 817

Redox rxns are usually what type of reactions?

Metabolic processes that are redox reactions?

Answer 817

Single displacement - free elements have oxidation state of 0, can change when bonded in a compound

Combustion - hydrocarbon + oxygen = CO₂ + water

Combination - A + B –> AB

• Glycolysis- NAD+ reduced, multiple C=O double bonds created
• Citric acid cycle, electron transport chain
• Beta-oxidation

Question 818

Balancing Redox Reactions (half reactions)

Answer 818

Neglect elements not being oxidized or reduced

1. write half reactions, one for reduction of element and one for oxidation of element
2. Assign oxidation states
3. Balance half reactions (except oxygen and hydrogen)
4. Balance oxygen by adding H2O
5. In acidic conditions, balance eqn by adding H+
   
   1. in basic conditions, add H+ then equal amounts of OH on both sides, combining them to make H2O and cancelling out
6. Add electrons to balance charge
7. Multiply both half equations to make electrons equal on both sides
8. Combine half reactions and cancel

Question 819

Redox titrations

Answer 819

Colorimetric indicator that indicates when oxidation/reduction has occured - usually use manganese

• permanganate ion is purple, manganese cation is colorless

Att equivalence point, reaction turns purple, no more reactant to be oxidized or reduced

• number of moles equal (e donated by one and absorbed by the other)

Normality of redox rxns: instead of [H+] and [OH-] conc, use the number of e’s gained or lost (picture) as “n”

n₁M₁V₁ = n₂M₂V₂

Question 820

Standard Reduction Potential

Answer 820

Tendencies for atoms to be reduced in any redox reduction half reaction (E°)

• measured in volts, relative to each other
  
  • the more positive an E° is, the more spontaneous the reduction
  • the more negative, the more nonspontaneous the reduction

**Any half reaction can be reversed to form the oxidation half rxn, reaction that is more spontaneous ISNT reversed

• also reverse sign of E°
• add two potentials for standard potential of full rxn

Don’t need to balance eqn, not affected by stoichiometric constants

Question 821

Electrochemical cells

Two types of electrochemical cells

Answer 821

Electrochemical cells: a device set up to harness a redox reaction to generate or use electrical energy

• all have anode - oxidation half reaction
• and cathode - reduction half reaction

Galvanic and electrolytic cells

***Electrons move from anode and are liberated via oxidation to the cathode, where they reduce the species in solution

Question 822

Galvanic Cells

Answer 822

A spontaneous redox reaction is used to generate a positive potential difference that drives a current

• Standard Reduction Potential (E°) is always positive (spontaneous rxn)

Anode and cathode consist of metals used in half reactions (grow and shrink)

To calculate direction of spontaneous reaction:

1. Identify which half reaction has higher reduction potential, this will be the CATHODE SIDE

• Other half reaction will be ANODE which is the site of oxidation
  
  • FLIP the anode half reaction and its sign
• Left with reduction and oxidation potential, which you can add to get E° (if this is negative, its incorrect)

Question 823

Daniell Cell

Answer 823

Galvanic cell example - cathode and anode half reactions are separated

Anode and cathode half cells connected by conductive wire and by a salt bridge: allows ions not participating in redox to travel from one solution to another

• these ions equalize the charge that is changed by the conductive wire (anode becoming more positive & vice versa)

Question 824

Concentration cell (galvanic cell)

Answer 824

Cathode and anode half reactions aren’t physically separated

Electrodes are same material

Two different molar concentrations

Question 825

Electrolytic cells

Answer 825

Energy put into system to drive a nonspontaneous redox rxn = negative E_{cell values}

• name electrolytic infers these reactions are often to break down compounds into parts with electrical energy
  
  • ex. 2H₂O –> 2 H₂ + O₂

Two electrodes: ***anode (+) and cathode(-) (usually just conductive metal)

• BECAUSE ANODE IS + AND CATHODE IS -, REQUIRES ENERGY TO PUSH ELECTRONS
  
  • Hydrogen produced at cathode (site of reduction, H is reduced from +1 to 0)
  • Anode is still oxidation site, this is where oxygen is produced

Same reactions can be used for both cell types, **But net reaction and sign will be flipped

Question 826

Electroplating

Question 827

Rechargeable batteries

Answer 827

Use both galvanic and electrolytic cells

• can either discharge spontaneously(galvanic) or recharge (electrolytic)

Lead acid battery- low energy to mass ratio (bulky battery), still used today

• in charged state, has PbO₂ electrode and Pb electrode in acid solution
  
  • reactions are flipped for charge and discharge

Nickel cadmium battery

Question 828

What does Nernst Equation help with?

Answer 828

Tells us how electric potential of a cell is affected by real world conditions, temperature and concentration of reactants

E’_cell = E°_cell - RT/zF (lnQ)

Q is inversely proportional, when [products] goes up, electric potential goes down (less spontaneous)

Question 829

Fluid definition

Answer 829

Any substance that can change its shape to match that of container

• **gases and liquids are fluids

Question 830

Density (p)

what is the density of water

Answer 830

p = m/v [kg/m³]

g/cm³ = g/mL (1L = 1000cm³)

density of water is 1 g/mL at 4°C and 1atm

Question 831

Specific gravity

Answer 831

Density of a liquid relative to water; unitless (ratio)

Specific gravity= p_(Water)/ p_(liquid)

• useful for modeling buoyancy

Question 832

Pressure equation

SI unit of pressure

PSI units

how do mmHg units work?

atm =

Answer 832

P = F / A [N/m²] = Pascal (Pa) = SI unit

Same force on a very small area is how knives cut things

PSI= pounds per square inch, same as Pascals but non metric: [lbs/in²]

mmHg is measuring pressure difference between two fluids by using difference in height of mercury in U shaped container

atm = average pressure exerted by atmosphere at sea level = 1 atm

Remember:

1 atm = 101,000 Pa = 760 mmHg** = 14.7 psi = 760 Torr = 1 bar

Question 833

Hydrostatic pressure

Answer 833

Pressure exerted on an object submerged in fluid

• P_sub = p gh

= (density of fluid) x (acceleration due to gravit) x (height of fluid above object)

Question 834

Absolute pressure

Answer 834

Pressure of a liquid on an object as well as atmospheric pressure above it

P_absolute = P_atmospheric + P_hydrostatic

*atmospheric pressure is higher at lower altitude

Question 835

Gauge Pressure

Answer 835

When measuring pressure (like blood pressure, tire pressure)

P_gauge = P_system - P_atmospheric

Question 836

Buoyancy

Buoyant Force

Answer 836

Whether something floats or sinks in fluid

• degree to which an object is submerged in water is proportional to its specific gravity (density relative to water)

If an object has a specific gravity of .92 (like ice), 92% of the object will be submerged in water

%submerged = p_object / P_liquid x 100

Buoyant force (exerted by water upwards on object)= pVg

• p = density of water
• V = volume of object
• buoyant force is proportional to volume of displaced water

Question 837

Pascal’s Law

Answer 837

A change in pressure at any location in an enclosed fluid is transmitted equally to all points throughout fluid

• how hydraulic lifts work

F₁/A₁ = F₂/A₂

If A₂ is greater, F₁ is smaller

Question 838

Surface Tension

Equation

Answer 838

Why does a liquid hold together? presence of intermolecular forces (like H-bonding in water)

In middle of water, each molecule has same amount of attractive forces on all sides

• Surface tension: **at the interface between air and water at the surface, the water molecules forces act unevenly on the ones at the surface and has no interactions with the air molecules
  
  • this imbalance of forces creates tension

Surface tension = Force / Length (N/m)

• Systems want to minimize surface tension because it has higher energy
  
  • this is why like dissolves like and raindrops fall in their shape

Question 839

Cohesion forces

Adhesion forces

Meniscus

Answer 839

Effect of intermolecular forces within a given substance causing them to stick together

Adhesion forces are molecules sticking to another type of molecule

• if adhesive forces are stronger than surface tension forces, liquid will crawl up walls of container and surface is curved (concave)
  
  • if fluid acts more strongly with itself than walls of container, has a convex shape

Question 840

Capillary Action

Answer 840

With a narrow enough tube so that adhesion forces are much greater than surface tension, can get liquid to rise up the tube in opposition to gravity

• how plants utilize water, thin layer chromatography

Question 841

Study of how fluids flow

Viscosity

Laminar Flow vs Turbulent Flow

Answer 841

Fluid dynamics

Viscosity: liquids resistance to flow (Pa x sec) (pressure x time)

• all fluids are viscous
• decreases as temperature increases
• releases energy

Laminar Flow: flowing fluid composed of parallel layers that may be moving at different velocities

Turbulent flow: flowing fluid composed of mixed layers that vary in pressure and speed

• the higher the velocity, the more likely the flow is to become turbulent

Question 842

Poiseuille’s Law

Answer 842

Flow rate = ∆pressure drop and radius over length

• large pressure drop causes flow rate to increase
• increasing radius dramatically increases flow right

Question 843

Bernoulli’s Law (fluids)

**when theres a change in height of container

Answer 843

Highly Idealized fluids- assume laminar flow, neglect viscosity and interactions between the fluid and container

P₁ + 1/2pv₁² + pgh₁ = P₂ + 1/2pv₂² + pgh₂

Energy in 3 forms: Pressure exerted on walls of container, Kinetic energy and potential energy in equation

** at a constant height, increasing velocity will decrease pressure exerted on container

Question 844

Continuity Equation (fluids)

relates to what biological process

Answer 844

Within a closed system, the flow rate of a liquid constant;

Fluids are incompressible, flow rates must be equal in a closed system

• Q1 = Q2

Since Q = vA

• v₁A₁ = v₂A₂

Relates to blood flow in circulation; Q in aorta will be equal to Q in the capillaries as a whole, which will have slower velocity but much higher surface area

Question 845

Venturi Effect

Answer 845

The narrower the tube, the lower the pressure

(look more into this)

Question 846

Periodic Motion

amplitude

period and frequency

Answer 846

Object is displaced relative to a midpoint in both the forward and backward directions - pendulum

• if it weren’t for friction and air resistance, motion would be continuous

Amplitude: displacement in (+) and (-) direction from midpoint; values are equal (|A|)

Period (T): time interval motion repeats

Frequency (f): how frequently motion occurs

• 1/T (s^-1) Hertz

Forms a sinuisodal curve on a graph

• being out of phase: same frequency and amplitude but not synced up

Question 847

Cycle of Periodic Motion

Two basic components

Periodic motion involves constant interchange between…

Answer 847

Inertia: an object in motion tends to stay in motion

Restoring Force: brings the object back to its equilibrium

• for a pendulum, this is gravity

Constant interchange between kinetic energy and potential energy (mgh)

• at midpoint, KE is maximized and PE = 0
• at extremes KE = 0 and PE is maxed

Question 848

Springs (Hookes Law)

Answer 848

Displacement is horizontal, spring oscillates back and forth

Hooke’s Law: F = kx

k = spring constant

x = displacement

If F= -kx, F is referring to the restoring force

Question 849

Pendulum and springs period equation

Answer 849

Pendulum:

T = 2π √ (L/g)

L = length, g = gravity

Springs:

T = 2π √ (m/k)

Question 850

Waves are

2 types of waves:

Answer 850

Periodic motion that propagates through space

Mechanical and Electromagnetic waves

mechanical: physical piece of mass that moves back and forth

• pendulum, spring

Electromagnetic waves: oscillating electromagnetic fields

• light

Question 851

Two types of mechanical waves:

Answer 851

Depends on direction particles are displaced, parallel or perpendicular to the direction of the wave

Transverse: physical components of wave move vertically, while wave moves horizontally (perpendicular)

• wavelength (λ): distance between peaks or troughs
• light

Longitudinal: particles propagate parallel to direction of wave (pushing and pulling motion)

• compression waves
  
  • amplitude = level of compression
• sound waves

Question 852

Velocity of waves is affected by…

Velocity of wave eqn

Answer 852

The medium it propagates through

v = λf

• m/s = m/s² (s^-1)

Question 853

Wave interference

Answer 853

When waves overlapm, they create a new wave with amplitude equal to the sum of their original amplitudes

Constructive interference: amplitudes align (are pointed in same direction), new wave has greater magnitude

Destructive interference: waves cancel each other out

Question 854

Standing waves

examples

Answer 854

Many waves overlapping and interfering with each other in a consistent manner

When graphed, sinuisodal graph with points of no displacement = nodes

Antinodes: points of maximum displacement

• 1 λ = 2 antinodes

Resonance frequency: object’s natural vibration frequency enabling maximum amplitude

Examples:

pipes and strings

Question 855

Harmonics of strings

Answer 855

1st harmonic: Standing wave on a string with only one antinode is lowest frequency

• wavelength is twice the length of string (1 wavelength is two antinodes)

2nd harmonic: two antinodes, wavelength = length of string

3rd harmonic: 3 antinodes, 1.5 wavelengths

λ = 2L / N

Question 856

Standing waves and pipes

Answer 856

Each end of pipe can be either closed or opened - closed ends have a node

• open ends have an antinode

If a pipe is open at both ends, has two antinodes

• can use same equations as those used for a string attached at both ends (harmonics)

** N = nodes instead of antinodes with strings

** come back to this video

Question 857

Gibbs Free Energy (∆G)

∆G° = standard free energy

Answer 857

Amount of energy available in a system that can be used for work on its surroundings

• ∆G indicates how spontaneous a reaction will be
  
  • (-): spontaneous and exergonic
  • (+): nonspontaneous and endergonic

∆G° = free energy at 273.15 K, 1 atm, 1 molar conditions

∆G = ∆G°​ + RT lnQ

** In non spontaneous biological reactions, pathway will shunt out product so that reaction shifts towards making more product

Question 858

Coupling Reactions (additivity)***

commonn biological mechanism

Answer 858

Coupling with nonspontaneous (endergonic reactions) with spontaneous (exergonic) to drive nonspontaneous rxns forward

• product of endergonic reaction is the reactant of exergonic (intermediate)
  
  • pulls out product quickly so that reaction is driven forward

Add ∆G values for each to obtain free energy of entire process

• **if overall ∆G is negative, whole process is spontaneous

Common mechanism:

Powering nonspontaneous reactions via ATP hydrolysis (HIGHLY spontaneous)

Question 859

4 basic forces of nature and why protons stick together and don’t attract its electrons

Answer 859

4 Basic Forces of Nature:

1. electromagnetic
2. gravitational
3. strong nuclear
4. weak nuclear

Strong nuclear force: holds protons together in the nucleus, stronger than the electromagnetic force that would normally drive them apart

• in this bound state, protons are more stable, energy difference is dissipated by nuclear binding energy

Question 860

Mass Defect (binding energy and mass)

Relationship between binding energy and defect

Answer 860

Binding energy and mass: MASS DEFECT of an atom: mass of a nucleus is less than that of its individual constituents

• small amount of mass is transformed into binding energy

When nucleus dissassembles into smaller units, the binding energy is amount of energy input required

E = MC²

binding energy = mass (speed of light)²

• all objects with mass have energy
• m = mass defect (difference between unit mass and individual constituent mass)

This is the energy associated with nuclear power, binding and splitting atoms

Question 861

Why are protons and electrons not attracted to each other within an atom?

Answer 861

Electrons have particle and wave-like properties (like all matter);

λ = h / mv

h = planck’s constant (6.62 x 10^-34 Jxs)

Question 862

Photoelectric effect (einstein)

Answer 862

Light shone on a metal surface causes electrons to be emitted from the metal

• when photons hit the surface of a metal, excite metallic electrons to higher energy states and move further from their nucleus, eventually ejecting from their atoms

Requires energy = Work Function (Φ)

• incident photon has to have at least the energy of the work function to emit an electron
  
  • E_kinetic = hf - Φ

KE = plancks constant x freq of light - (work function)

• kinetic energy of the electron emitted is the leftover energy past the threshold of the work function

Question 863

isotopes

Answer 863

Isotopes: atoms with same number of protons but different number of neutrons

Question 864

Nuclear reactions

4 types to know

Answer 864

Any reaction involving particles in the nucleus

• Fusion
• Fission
• Nuclear Decay
• Transmutation- the reverse of nuclear decay, only in lab settings

Question 865

Nuclear fusion

Answer 865

Two or more nuclei are forced together by extremely high levels of energy(like the sun), causing them to merge into new larger nucleus

• releases a lot of energy due to dissipation of binding energy of larger nucleus
• produces a neutron

Question 866

Nuclear fission

Answer 866

Large nucleus split into 2 or more nuclei

• no nuclear particles lost

Question 867

Radioactive decay

3 types

Answer 867

Unstable isotopes break down and eject mass, energy or photons

1. Alpha decay- emission of an alpha particle (2 protons and 2 neutrons)
   
   1. decrease in atomic number by 2 and atomic mass by 4
      
      1. emitted particles interact with matter and can be dangerous to tissue
         
         1. can be easily shielded against and don’t break skin or clothing
2. Beta Decay- 2 forms
   
   1. ​Beta minus: neutron converted to proton and electron is ejected
      
      1. atomic number increases, mass doesn’t change
   2. Beta plus: proton converted to neutron and positron is ejected
      
      1. atomic number decreases, mass doesn’t change
3. gamma decay
   
   1. ​emission of high energy photon (gamma ray) from an excited nucleus
      
      1. gamma rays have no mass or charge

Question 868

Electron capture

Answer 868

Nucleus absorbs an electron which merges with a proton to form a neutron

• atomic number decreases, weight unchanged

Electron + proton = neutron

Question 869

Half-life

Answer 869

Timing of radioactive decay so predictable can be used to determine age of rocks and artifacts (carbon dating)

Half life- amount of time for half of existing material to decay

• ex. every 5 miniutes, half of the existing material decays

N_t = N₀(1/2)^t/t_1/2

amount of radioactive material at time (t) equals original amount times .5 to the power of half lives that have passed; if half life is 2 years, after two years = .5²