1 - CELL AND MOLECULAR BIOLOGY

Question 1

define electronegativity

Answer 1

ability of an atom to attract electrons

Question 2

what are the 3 main type of chemical bonds

Answer 2

ionic

covalent

hydrogen

Question 3

what are ionic bonds?

Answer 3

transfer of electrons between atoms of differing electronegativity

the one with a higher electronegativity, takes the electrons

Question 4

what are covalent bonds?

Answer 4

sharing of electrons

atoms can be single/double/triple -bonded

Question 5

what are non-polar covalent bonds?

Answer 5

equal sharing of electrons between two atoms of similar electronegativity

Question 6

what are polar covalent bonds?

Answer 6

unequal sharing of electrons between two atoms of differing electronegativity

FORMS A DIPOLE!!

Question 7

what are van der waal interactions?

Answer 7

weaker and more transient than hydrogen bonding. more of an interaction which gets stronger, the larger the molecule is

Question 8

what are hydrogen bonds?

Answer 8

weak interaction between a hydrogen (attached to a highly electronegative atom) and a negatively charged atom of another molecule (F, O, N)

Question 9

what are the 5 most important properties of water?

Answer 9

it’s a good solvent

it has a high heat capacity

ice floats. water expands as it freezes and becomes less dense

it has strong cohesion/surface tension. its strong cohesion between H2O molecules produces high surface tension

it has adhesion. adheres to unlike objects - water sticks to skin/glass

Question 10

why is water a good solvent?

Answer 10

the dipoles (the slight positive and negative charges) of H2O break up charged ionic molecules, by disrupting the attractive forces between the atoms of that molecule

this makes it easier for water to dissolve substances

Question 11

why does water have a high heat capacity?

Answer 11

due to the hydrogen bonds between water molecules which require (the absorption) heat to break

Question 12

what is heat capacity?

Answer 12

the amount of heat needed to change the temperature of a substance by 1 unit (e.g. 1 degree)

Question 13

why does ice float?

Answer 13

water expands as it freezes and becomes less dense

the H-bonds become rigid and forms a crystal that keeps molecules separated. their attractions arrange them into fixed positions

Question 14

why is there strong cohesion between water molecules?

Answer 14

due to H2O’s ability to form hydrogen bonds - and the extremely electronegative oxygen and the comparatively positive hydrogen

Question 15

why does water possess the adhesive property?

Answer 15

due to H2O’s polar nature, it can also attract “unlike” structures. it’s attracted to substances with charges

Question 16

what are minerals?

Answer 16

inorganic ions the body needs to function

can be found intracellularly and extracellularly

Question 17

what are vitamins?

Answer 17

organic molecules the body needs to function

Question 18

what are the (2) major categories of vitamins? when consumed in excess, where are they stored?

Answer 18

fat-soluble
- deposited in body fat; overconsumption can lead to toxic levels in the body

water-soluble
- excreted in the urine

Question 19

what is vitamin B? describe it

Answer 19

a water-soluble vitamin

8 types of vitamin B

vitamin B usually functions as coenzymes or their precursors in metabolic processes – also important in blood synthesis

Question 20

what is vitamin C? describe it

Answer 20

a water-soluble vitamin

vitamin C is necessary for synthesizing collagen, an important structural protein, thus a deficiency in vitamin C can lead to scurvy (if the collagen structure is less stable, we get weakened connective tissues)

Question 21

what are the (2) important water-soluble vitamins?

Answer 21

B and C

Question 22

what are the (4) important fat-soluble vitamins?

Answer 22

A, D, E, and K

Question 23

what is vitamin A? describe it

Answer 23

a fat-soluble vitamin

important for:

• vision (visual pigmentation)
• epithelial (skin) maintenance

Question 24

what is vitamin K? describe it

Answer 24

a fat-soluble vitamin

important for blood clotting. it produces proteins involved in the process

Question 25

what is vitamin D? describe it

Answer 25

a fat-soluble vitamin

regulates calcium and phosphorous levels by promoting its absorption from the intestine

synthesized by the skin in the presence of sunlight

Question 26

what is vitamin E? describe it

Answer 26

a fat-soluble vitamin

an antioxidant which prevent cell damage by neutralizing free radicals which (highly unstable unpaired electrons which can destroy cells)

Question 27

what are the key properties of hydroxyl (OH) groups?

Answer 27

polar and hydrophilic

generally a strong base. but can be acidic depending on conditions

Question 28

what are the key properties of carboxyl (COOH) groups?

Answer 28

polar, hydrophilic, weak acid

Question 29

what are the key properties of amino (NH2) groups?

Answer 29

polar, hydrophilic, weak base

Question 30

what are the key properties of phosphate (PO4 -3) groups?

Answer 30

polar, hydrophilic, acid

Question 31

what are key properties of carbonyl (C=O) groups?

Answer 31

polar and hydrophilic

Question 32

what are key properties of methyl (CH3) groups?

Answer 32

non-polar and hydrophobic

Question 33

what are the 3 disaccharides you need to know for the exam? list what monosaccharides are combined

Answer 33

sucrose: glucose + fructose

lactose: glucose + galactose

maltose: glucose + glucose

Question 34

in a disaccharide, what joins the two monosaccharides?

Answer 34

glycosidic linkage

Question 35

briefly describe the reactions of dehydration synthesis and hydrolysis

Answer 35

monomers combine together to form polymers via dehydration synthesis. water is formed during this process.

polymers are broken down to form monomers via hydrolysis. water is consumed

Question 36

in a polymer, how are bonds broken and formed?

Answer 36

formed: dehydration synthesis; water is formed as by-product

broken down: hydrolysis; water consumed

this applies to all polymers, regardless of it’s a glycosidic linkage, a phosphodiester bond, or a peptide bond.

Question 37

what are the (2) types of glycosidic bonds?

Answer 37

alpha and beta

determined by the -OH groups of the sugars

Question 38

describe the alpha-glycosidic bond

Answer 38

between 2 alpha-monosaccharide molecules

the -OH groups forming the bond are both pointing down

Question 39

describe the beta-glycosidic bond

Answer 39

between an alpha and a beta-monosaccharide molecule

the bond is between an -OH pointing down and an -OH pointing up

Question 40

what are considered to be under carbohydrates?

Answer 40

saccharides, starch, glycogen, cellulose, chitin

Question 41

how are starch and glycogen similar and different?

Answer 41

both are polymers of alpha-glucose molecules (thus, have alpha-glycosidic bond)

they differ in their polymer branching and where they are found

glycogen has more branching

glycogen found in animal cells and starch found in plant cells

Question 42

where is starch found? what’s its function?

Answer 42

in plant cells

stores energy

Question 43

where is glycogen found? what’s its function?

Answer 43

found in animals

stores energy

Question 44

how does one differentiate between alpha and beta monosaccharides?

Answer 44

if the OH on the anomeric carbon is pointing DOWN, it’s alpha

if the OH on the anomeric carbon is pointing UP, it’s beta

Question 45

describe cellulose

Answer 45

a polymer of beta-glucose

a structural molecule for walls of plant cell and wood

Question 46

describe chitin

Answer 46

a polymer of beta-glucose that’s attached to a nitrogen containing group: (n-acetylglucosamine)

a structural molecule found in fungal cells and insects’ exoskeleton

Question 47

how are cellulose and chitin similar?

Answer 47

they are both comprised of beta-glucose molecules (but chitin also includes N-molecules)

thus, they both use beta-glycosidic bonds

Question 48

can humans digest glycosidic linkages?

Answer 48

our digestive system can digest only alpha-glycosidic linkages

they can’t digest beta-glycosidic linkages

• cows have bacteria in their gut that produces the enzymes that can break down beta-glycosidic linkages

Question 49

what are the macromolecules (polymers) and their monomer components?

Answer 49

carbohydrates (aka polysaccharides): monosaccharides

lipids: a bit complicated, but generally composed of hydrocarbons - lipids are not really considered polymers but are macromolecules

proteins (aka polypeptides): amino acids

nucleic acids (DNA/RNA): nucleotides

Question 50

briefly describe lipids. what bonds are seen in lipids?

Answer 50

long hydrocarbon chains that are non-polar and hydrophobic

they are not considered polymers bc they are not made of repeated units

covalent bonds between the hydrocarbons

Question 51

what are the general functions of lipids?

Answer 51

insulation: preserves heat

energy storage: energy reserves we can burn when needed

endocrine molecules (steroid hormones)

structural (phospholipids and cholesterol are key components of the cell membrane)

Question 52

what are triglycerides (triacylglycerols)

Answer 52

consists of 3 fatty-acid chains attached to a glycerol backbone (3 carbons). the fatty acids can be saturated or unsaturated

body converts calories it doesn’t need right away to triglycerides which are then stored in fat cells. later, hormones release them for energy (in between meals)

Question 53

differentiate between saturated and unsaturated fatty acid chains

Answer 53

saturated has no double bonds which lead to straight chains. these straight chains can stack densely and form plaques - bad for health

unsaturated has double bonds which lead to kinks in the chains. they stack less densely - good for health. can be cis/trans

Question 54

what are phospholipids (diacylglycerols)?

Answer 54

2 fatty-acids and a phosphate group (w/ +R) attached to a glycerol backbone

major component of cell membranes

they are amphipathic: has both hydrophilic and hydrophobic properties
- hydrophobic tail: fatty acids
- hydrophilic head: glycerol and phosphate group

Question 55

what are steroids? what are considered steroids?

Answer 55

contains 3 six-membered rings and 1 five-membered rings (4 rings in total)

e.g. hormones and cholesterol

Question 56

what’s the most common precursor to steroid hormones?

Answer 56

cholesterol

Question 57

what are waxes?

Answer 57

esters of fatty acids and monohydroxy alcohol

used as protective coating of skin and exoskeletons

Question 58

what are carotenoids?

Answer 58

fatty acid carbon chain with conjugated double bonds and five/six-membered rings at each end

• includes pigments which produces colour in plants/animals

subgroups: carotenes and xanthophylls

Question 59

what are porphyrins? give 2 examples

Answer 59

4 joined pyrrole rings

often complexes with a metal in the center

• Fe in hemoglobin (from transporting O2)
• Mg in chlorophyll (for absorbing light)

Question 60

what are adipocytes?

Answer 60

specialized fat cells

major energy storage site in the body

Question 61

what are glycolipids?

Answer 61

similar to phospholipids, but instead of a phosphate group, they have a carbohydrate group

Question 62

what are lipoproteins?

Answer 62

bc lipids are insoluble, lipoproteins are used to transport lipids in the blood

lipoproteins are a lipid core surrounded by phospholipids (lipid bilayer) and apolipoproteins

Question 63

how does the cell membrane maintain its fluidity in different temperatures?

Answer 63

by changing membrane fatty acid composition

the cell membrane becomes more rigid in cold weather. to avoid rigidity, the cell membrane has cholesterol (prevents tight packing of phospholipids) and mono/polyunsaturated fatty acids incorporated into the membrane which increases fluidity

the cell membrane becomes more fluid and flexible in warm weather. to prevent itself from collapsing, cholesterol is added to restrict movement. the fatty acids become more saturated, allowing it to densely stack itself, increasing rigidity.

Question 64

describe the general structure of an amino acid

Answer 64

a amino group, carboxyl group, a hydrogen group, and a R-side chain linked to an alpha-carbon

Question 65

what functions do proteins have?

Answer 65

structural (e.g. collagen)

mechanical/movement (e.g. actin/myosin)

enzymes

hormones (e.g. insulin)

antibodies

fluid balance

acid-base balance - pH (albumin)

channels/pumps

transport (e.g. hemoglobin which moves oxygen)

storage (e.g. casein which stores amino acids in mammalian milk)

Question 66

what do enzymes do? what do they not do?

Answer 66

catalyze reactions in both forward and reverse directions – lower the activation energy required for a reaction, accelerating the rate of the overall reaction.

they do not change the spontaneity of a reaction or the equilibrium

they have varying function based on pH and temp

Question 67

what determines the efficiency of an enzyme?

Answer 67

temperature (it can cause denaturation), the ideal temperature for enzymes can vary. but as you raise temperature, you generally see an increase in enzyme activity and reaction rate due to the increase in kinetic energy, having molecules bounce around more quickly. BUT, if temperature raised too high, the enzyme will denature and lose its function

pH (it can cause denaturation), the ideal pH for enzymes vary
- e.g. pepsin prefers low pH
- urease and trypsin prefer moderate pH

substrate and enzyme concentration

presence/absence of inhibitors

Question 68

what does amylase do?

Answer 68

catalyzes reaction that breaks the alpha-glycosidic bonds in starch

Question 69

all enzymes are considered proteins, except..?

Answer 69

RNA enzymes / ribozymes / riboenzymes

Question 70

what type of proteins are there?

Answer 70

storage, transport, enzymes

Question 71

what are cofactors?

Answer 71

non-protein molecules that assist enzymes, usually by donating or accepting some component of the reaction, such as electrons or functional groups

some bind reversibly or some permanently

Question 72

what’s a holoenzyme?

Answer 72

cofactor + protein

Question 73

what’s a apoprotein/apoenzyme?

Answer 73

when an enzyme is not combined with a cofactor but requires it for activity

Question 74

what’s a coenzyme?

Answer 74

an organic coenzyme, like vitamins

enzymes can also be inorganic (like metals, Fe2+ or Mg2+)!

can be categorized into prosthetic group (bind covalently) and cosubstrates (bind reversibly)

Question 75

in regards to enzymes, what’s a prosthetic group?

Answer 75

if a cofactor is covalently or tightly bound to an enzyme

Question 76

what are simple proteins?

Answer 76

proteins formed entirely of amino acids

Question 77

what are the (2) types of simple proteins?

Answer 77

albumins & globulins: functional proteins that act as carriers or enzymes

scleroproteins: fibrous proteins with a structural function (e.g. collagen)

Question 78

what are conjugated proteins?

Answer 78

a simple protein linked to a non-protein

Question 79

what are (5) types of conjugated proteins?

Answer 79

lipoprotein: bound to a lipid

mucoprotein: bound to a carbohydrate

chromoprotein: bound to a pigmented molecule

metalloprotein: protein complexed around a metal ion

nucleoprotein: contains histone or protamine, linked to a nucleic acid

Question 80

what are the different levels of protein structures? describe them

Answer 80

primary: sequence of amino acid, connected by peptide bonds

secondary: the 3D shape from hydrogen bonding between the carboxyl and amino groups of amino acids, side-by-side (involves the peptide backbone)

tertiary: 3D structure mainly from non-covalent interactions between the R-groups of amino acids

quaternary: 3D shape of a protein that is a grouping of 2 or more, separate peptide chains

Question 81

how is the primary structure of a protein determined?

Answer 81

sequence of nucleotides in the mRNA determine the sequence of amino acids

Question 82

what are the types of secondary structures of proteins?

Answer 82

alpha-helix

beta-sheet

Question 83

when talking about the non-covalent interactions that hold the tertiary structure of a protein together, what does it include? (5)

Answer 83

hydrogen bonds

ionic bonds

hydrophobic effect/interaction: R-groups push away from water

disulfide (covalent interaction, an exception): between cysteines

van der waals forces

Question 84

what are the (3) main protein categories?

Answer 84

globular

structural/fibrous

membrane

Question 85

describe globular proteins

Answer 85

water soluble

mainly tertiary structures

diverse range of functions

enzymes are globular !!

Question 86

describe structural/fibrous proteins

Answer 86

not water soluble

mainly secondary structures

long polymers

function: to maintain/add strength to cellular/matrix structures

e.g. collagen or keratin

Question 87

describe membrane proteins

Answer 87

not water soluble

includes proteins that function as membrane pumps, channels, or receptors

Question 88

what is protein denaturation?

Answer 88

when a protein reverts back to its primary structure

Question 89

give (4) examples of denaturing agents

Answer 89

temperature, pH, UV light/chemical, and salt concentrations

Question 90

a protein’s function is determined by what?

Answer 90

its overall shape! aka 3D structure

when denatured, it won’t be able to function properly

Question 91

can protein denaturation be reversed?

Answer 91

generally irreversible, but in some cases, can be reversed by removing the denaturing agent

Question 92

what does protein denaturation imply about the protein’s information?

Answer 92

all information needed for a protein to assume its folded, functional (native) form is encoded in its primary structure

Question 93

differentiate between protein denaturation and digestion

Answer 93

denaturation reverses a protein to its primary structure

digestion eliminates all protein structures, including primary

Question 94

what are the functions of nucleic acids?

Answer 94

to encode, express, and store genetic information

Question 95

how are the strands of DNA connected?

Answer 95

via base pair

hydrogen bonds that occur between nucleotides on opposite strands

Question 96

how are nucleotides bonded?

Answer 96

phosphodiester bond between the phosphate group of one nucleotide and the five-carbon sugar of another

Question 97

describe the structure of nucleotides

Answer 97

nitrogenous base, a five-carbon sugar, and a phosphate group

Question 98

differentiate between nucleosides and nucleotides

Answer 98

a nucleoside does not have a phosphate group

nucleotide: nitrogenous base, sugar, phosphate group

nucleoside: nitrogenous base, sugar
- e.g. “adenosine” instead of “adenine”

Question 99

what are the nitrogenous bases for DNA and RNA?

Answer 99

DNA: guanine, cytosine, adenine, thymine

RNA: guanine, cytosine, adenine, uracil

Question 100

in DNA and RNA, which nitrogenous base pairs with what? and how many bonds? what does that implicate

Answer 100

GCAT -> GC AT

guanine and cytosine - 3 hydrogen bonds

adenine and thymine - 2 hydrogen bonds

since G and C have more hydrogen bonds, they require a higher (melting) temperature to break

the same goes for RNA, just replace thymine with uracil

Question 101

which of the nitrogenous bases are purines? pyramidines?

Answer 101

purines: guanine, adenine

pyrimidines: cytosine, thymine, uracil

Question 102

differentiate between the structures of DNA and RNA

Answer 102

DNA: GCAT
RNA: GCAU

DNA: has deoxyribose sugar (missing an O on C2). it’s double helix, with 2 strands that are anti-parallel (both run 5’ to 3’ but in opposite directions)

RNA: has ribose sugar. USUALLY single stranded

Question 103

in regards to DNA, why is the direction called “ 5’ to 3’ “ ?

Answer 103

phosphate is attached to C5 of the deoxyribose sugar and the OH group is attached to C3

looking at DNA we see that the phosphate (at C5) begins the sequence and the OH (at C3) ends it

Question 104

what is chargaff’s rule?

Answer 104

the number of purines = the number of pyrimidines because they are base paired

A + G = T + C

A = T
G = C

Question 105

describe the discovery of the cell. who? how?

Answer 105

robert hooke was the first to discover cells when he looked at a piece of tree bark under a microscope and observed the cell walls of dead plant cells

a decade later, van leeuwenhoek enhance the magnification of microscope lenses and was the first to observe living cells

Question 106

what does the Cell Theory state (3+4=7)?

Answer 106

all living organisms are composed of 1 or more cells

the cell is the basic unit of function, structure, and organization in all organisms

all cells come pre-existing, living cells

NEW TENANTS FROM THE MODERN INTEPRETATION OF THE CELL THEORY:

activity of an organism depends on the total activity of independent cells (each cell contributes to the overall activity of an organism)

energy flow occurs within cells (cells have a functional metabolism)

cells carry hereditary information

all cells have similar basic composition among similar species

Question 107

what characteristics are shared by all cells?

Answer 107

bound by plasma membrane: a selective barrier that separate its contents from the outer environment

contains genetic material (DNA)

contains ribosomes: synthesizes functional proteins from genetic material (RNA)

Question 108

describe the RNA World Hypothesis theory. what does it state/believe? why? backed by what?

Answer 108

suggests that RNA was the precursor of current life (based on DNA, RNA, and proteins)

states that RNA stores genetic information like how DNA does, catalyzes chemical reactions like how enzymes do - a reason behind the belief that RNA played a major role in the evolution of cellular life

also backed by the fact that RNA is more unstable than DNA, due to its extra hydroxyl group which makes it more likely to participate in chemical reactions

Question 109

what does the Central Dogma of Genetics (a theory) state?

Answer 109

states that information must travel from DNA -> RNA -> protein

cannot travel backwards from protein! information however, can travel back and forth between DNA and RNA in special cases

Question 110

describe the stereomicroscope. what are the pros and cons?

Answer 110

uses visible light to view the surface of a sample

pros: can view living samples

cons: has low light resolution compared to a compound microscope

Question 111

describe the compound microscope. what are the pros and cons?

Answer 111

uses visible light to view a thin section of the sample

pros: can view some living samples (single cell layer)

cons: may require staining for good visibility which kills cells - samples that are thin enough don’t require staining

Question 112

describe phase contrast microscope. what are the pros and cons?

Answer 112

uses light phases and contrast for a detailed observation of living organisms. including internal structures if thin

pro: good resolution and contrast

cons: not ideal for thick samples. produces a “halo” effect around the perimeter of the samples

Question 113

describe the confocal laser scanning microscope and fluorescence. what are the pros and cons?

Answer 113

used to observe thin slices while keeping a sample intact

pros: can observe specific parts of a cell via fluorescent tagging

cons: can cause artifacts - not naturally present and caused by the process

note: can be used with light instead of fluorescence

Question 114

what is a common microscopy method used to observe chromosomes during mitosis?

Answer 114

confocal laser scanning microscope and fluorescence

Question 115

describe scanning electron microscope (SEM)? what are the pros and cons?

Answer 115

shoots electrons across the surface of a specimen, allowing high definition image

pros: view surface of 3D objects with high resolution

cons: can’t use on living samples as the preparation kills samples. preparation is extensive as samples need to be dried and coated. and is costly

Question 116

describe cryo scanning electron microscope (Cryo SEM). what are the pros and cons?

Answer 116

similar to SEM

pros: sample is not dehydrated, so you can observe samples in their more “natural” form

cons: can’t be used on living samples. samples must be frozen, which might cause artifacts

Question 117

describe transmission electron microscope (TEM). what are the pros and cons?

Answer 117

electron beams passed thru a thin section of the sample, producing very high resolution 2D images. can see internal structures - not just tissue and cells

pros: can observe very thin cross-sections in high detail, and can observe internal structures with very high-resolution

cons: cannot be used on living samples. requires extensive preparation (samples must be dehydrated, fixed into resin, and sliced into thin sections) and is costly

Question 118

which microscope has the highest magnification?

Answer 118

transmission electron microscope (TEM)

Question 119

describe electron tomography. what are the pros and cons?

Answer 119

not a type of microscope, but a technique used to build a 3D model of the sample via TEM (transmission electron microscope) data

pros: can look at objects in 3D and see objects relative to one another

cons: same as TEM cons: cannot be used on living samples. requires extensive preparation and is costly

Question 120

what is centrifugation?

Answer 120

common technique used to prepare sample for observation or further experimentation

it spins and separated liquified cell homogenates into layers based on density

Question 121

in centrifugation, what is the order in which cells separate?

Answer 121

most dense to least dense

most dense will pellet to the bottom and so on

Question 122

in differential centrifugation that deals with organelles, which parts are expected to separate first, to the bottom?

Answer 122

nuclei layer -> mitochondria/
chloroplasts/lysosomes ->
microsomes/small vesicles ->
ribosomes/viruses/larger
macromolecule

Question 123

differentiate between differential centrifugation and density centrifugation

Answer 123

differential: density, shape, and speed
- spin, separate dense pellet, repeat

density: density

Question 124

what should be noted about solubility in differential centrifugation?

Answer 124

differential centrifugation forms continuous layers of sediment, where insoluble proteins are found in pellet and soluble proteins remain in the supernatant, liquid above the pellet

Question 125

differentiate between anabolic and catabolic processes/reactions

Answer 125

anabolic: small molecules assembled into bigger ones – requires energy

catabolic: large molecules broken into smaller ones – releases energy (CATACLYSM LOL!!!!)

Question 126

what is ATP?

Answer 126

a common source of activation energy

ATP stores its potential energy in the form of chemical energy.

ATP is an unstable molecule because the 3
phosphates in ATP are negatively charged and repel one another. when one phosphate group is removed via hydrolysis, a more stable ADP molecule results. the change from a less stable molecule to a more stable molecule always releases energy

it provides energy for all cells by transferring phosphate from ATP to another molecule

Question 127

how is new ATP formed?

Answer 127

via phosphorylation

ADP and phosphate come together using energy from an energy-rich molecule, like glucose

Question 128

define Km and Vmax in regards to enzymes

Answer 128

Km: “michaelis constant”, represents the substrate concentration at which the rate of reaction is half of the max velocity (rate) of the enzyme, or Vmax

Vmax: max velocity (rate) of the enzyme

Question 129

what are allosteric enzymes?

Answer 129

they have both an active site for substrate binding AND an allosteric site for binding of an allosteric effector (can be an activator/inhibitor)

they can have multiple sites for regulatory enzymes to bind

Question 130

what is competitive inhibition? describe Km and Vmax in this situation

Answer 130

substance is an inhibitor (by mimicking the substrate) that binds at the active site, preventing substrates from attaching. this binding is reversible and brief

the effect of competitive inhibition can be combated by increasing concentration of substrate

competitive inhibitors increase Km (bc it directly interferes with how substrates bind) but Vmax remains the same

Question 131

what is non-competitive inhibition? describe Km and Vmax in this situation

Answer 131

substance inhibits enzyme by binding somewhere other than the active site, allowing the substrate to still bind, but the enzyme’s ability to catalyze a reaction has decreased and reaction doesn’t reach completion (bc the enzyme conformation has changed but the ability of a substrate to bind has not been)

all non-competitive inhibition is allosteric but not all allosteric is competitive inhibition

Kmax remains the same but Vmax decreased

Question 132

what is allosteric inhibition?

Answer 132

substance binds to enzyme (at the allosteric site, affecting the ability of the active site to function) and induces its inactive form

does not follow Km and Vmax trends

Question 133

what is uncompetitive / anti-competitive inhibition?

Answer 133

when an enzyme inhibitor binds to the enzyme-substrate (ES) complex – preventing the formation of the product

Question 134

describe the relationship between Km and binding affinity

Answer 134

recall, Km: the substrate concentration at which the rate of reaction is half of the max velocity of the enzyme, or Vmax

Km inversely represents binding affinity

a higher Km = worse substrate binding

lower Km = better substrate binding

Km and binding affinity are both intrinsic properties so increasing/decreasing substate/enzyme concentration doesn’t affect this property

Question 135

what is cooperativity, in regards to enzymes?

Answer 135

positive cooperativity: phenomenon where an enzyme becomes more receptive to other substrates after binding to a substrate at its active site

negative cooperativity: enzyme becomes less receptive to other substrates after binding to a substrate at its active form

cooperativity isn’t limited to enzymes can also be done by non-enzymes e.g. oxygen in hemoglobin

Question 136

what are the (3) classifications of membrane proteins?

Answer 136

peripheral: loosely attached to surface of one side of the membrane

integral: embedded in the cell membrane

transmembrane: type of integral; travels all the way through the membrane

Question 137

what are the (8) types of membrane proteins?

Answer 137

channel proteins

recognition proteins

ion channels

porins

carrier proteins

transport proteins

adhesion proteins

receptor proteins

Question 138

what are channel proteins?

Answer 138

proteins that provide a passageway through the membrane for hydrophilic (water soluble), polar, and charged substances

can also be done for substances that can normally diffuse, to allow the protein to regulate how much goes in, more quickly, etc (e.g. aquaporins for water)

Question 139

what are recognition proteins?

Answer 139

type of glycoprotein (has an attached oligosaccharide/carbohydrate) used to distinguish between self and foreign – healthy vs diseased – by immune cells

cell-to-cell recognition

Question 140

what are ion channels?

Answer 140

used to pass ions across the membrane

they can be open or gated (3 types) so there are 4 types overall

referred to as gated channels in nerve and muscle cells

Question 141

what are glycoproteins?

Answer 141

play a role in cell-cell recognition; immune cells can check membrane glycoproteins to identify if a cell is foreign or not

cell signaling: glycoproteins can act as receptors by binding to signalling molecules

used in cell adhesion by binding to molecules outside the cell help stabilize them

Question 142

what are the (3) different types of ion, gated channels?

Answer 142

voltage-gated: responds to difference in membrane potential to open/close

ligand-gated: chemical (signalling molecule) binds to open channel

mechanically-gated: responds to pressure or vibration

AND open channel

Question 143

what are porins?

Answer 143

allows the passage of certain ions and small polar molecules

increases the rate of water passing in kidney and plant root cells

tends to be less specific: if you can fit through the large passage, you can go through

Question 144

what are transport proteins?

Answer 144

proteins that transport materials across the membrane

they do this by active transport and facilitated diffusion (note that only active transport uses ATP)

Question 145

what are the types of transport proteins? (2)

Answer 145

carrier and channel

Question 146

what are carrier proteins?

Answer 146

allows for selective transport across the membrane via integral membrane protein

changes shape (undergoes conformational changes) after binding to specific molecule that enables it to be passed across - also changes shape to release it

Question 147

what’s the major difference between active transport and passive transport

Answer 147

active transport uses ATP

Question 148

what are adhesion proteins?

Answer 148

attach cells to neighbouring cells and provide anchors for stability via internal filaments and tubules

Question 149

what are receptor proteins?

Answer 149

these membrane proteins are binding sites for signalling molecules which then transmit changes to the inside of the cell

Question 150

what are the (3) major components/properties that contribute to the cell membrane? describe them

Answer 150

phospholipid membrane permeability: allows small, uncharged, non-polar, hydrophobic molecules to freely pass through the membrane. polar molecules may pass through if they’re small and uncharged (everything else requires a transporter)

cholesterol: adds rigidity to the membrane in normal conditions and maintains fluidity at lower temperatures

glycocalyx: carbohydrate coat; covers the outer side of the cell wall (in some bacteria) or plasma membrane (in some animal cells).

Question 151

what are the functions of the glycocalyx?

Answer 151

glycocalyx: carbohydrate coating on the outer side of the cell wall or plasma membrane

possible functions:

• adhesive capabilities
• barrier to infection and chemical/physical damage OR
• markers for cell-cell recognition

can be found on the inside of blood vessels where it helps to provide a protective barrier and maintains the vascular walls beyond the plasma membrane

Question 152

what does the glycocalyx consist of?

Answer 152

glycocalyx: carbohydrate coating on the outer side of the cell wall or plasma membrane

consists of glycolipids attached to the cell membrane AND glycoproteins that may serve as recognition proteins

Question 153

what performs the same role cholesterol does in animal cells’ membranes but in plant cells and prokaryotes?

Answer 153

cholesterol: adds rigidity to the membrane in normal conditions and maintains fluidity at lower temperatures

plant equivalent = sterols

prokaryotes equivalent = hopanoids

Question 154

what are the (4) main functions of the cell membrane?

Answer 154

acts as a barrier between the inside and outside of the cell

allows for communication with other cells

has selective permeability to regulate transport of substances in and out of a cell

provides structural support and protection

Question 155

what’s the fluid mosaic model?

Answer 155

a biological term used to describe the cell membrane

fluid: cell membrane components are constantly shifting around - even the phospholipids which frequently rotate and move laterally within the same layer (can even flip vertically into another layer)

mosaic: composed of multiple different parts (phospholipids and proteins)

Question 156

how are peripheral proteins held in place to a side of the cell membrane? how can this attachment be disrupted?

Answer 156

peripheral membrane proteins are generally hydrophilic and held together by hydrogen bonding and electrostatic interactions

this can be disrupted by changing salt concentration or pH

Question 157

how can integral proteins be detached from the membrane?

Answer 157

integral proteins are hydrophobic and can be detached using detergent

Question 158

differentiate between chromatin and chromosomes

Answer 158

chromosomes are tightly condensed chromatin when the cell is ready to divide

Question 159

how many chromosomes do humans have?

Answer 159

46

23 from their mother, 23 from their father

Question 160

what’s chromatin?

Answer 160

general packaging structure of DNA around proteins (histones) in eukaryotes

tightness in packaging depends on the cell stage

Question 161

what’s a histone?

Answer 161

proteins that provides structural support for DNA

Question 162

what’s a nucleosome?

Answer 162

a unit of DNA wrapped around 8 histones

Question 163

what’s the nucleolus?

Answer 163

found in the nucleus; the site of ribosome synthesis

Question 164

briefly describe the process of ribosome synthesis

Answer 164

rRNA synthesizes in the nucleus

ribosomal subunits are synthesized using rRNA and ribosomal proteins (imported from the cytoplasm).

once ribosomal subunits have formed, they’re exported to the cytoplasm for final assembly of a complete ribosome

Question 165

what is the substitute of cytoplasm in the nucleus? (what’s there instead?)

Answer 165

instead of cytoplasm, the nucleus has nucleoplasm

Question 166

describe the outer layer of the nucleus and what it uses for transport

Answer 166

the nucleus is bound by a double layer nuclear envelope with nuclear pores for transport (for mRNA, ribosome
subunits, dNTPs, proteins like RNA
polymerase and histones).

the double membrane means it has two phospholipid bilayers

Question 167

what is the nuclear lamina?

Answer 167

found in the nucleus of eukaryotic cells

a dense fibrillar network (intermediate filaments and membrane associated proteins) that provide mechanical support AND help regulate DNA replication, cell division, and chromatic organization

Question 168

differentiate between the nucleus and nucleoid

Answer 168

nucleus found in eukaryotic cells

nucleoids found in prokaryotes

Question 169

what’s the nucleoid?

Answer 169

for prokaryotes

contains all or most of the cell’s genetic material

Question 170

what’s the cytoplasm?

Answer 170

most of the cell’s metabolic activity and transport happens here

the area includes the cytosol and organelles

Question 171

what is cytoplasmic streaming?

Answer 171

the streaming movement within the cytoplasm

Question 172

differentiate between cytoplasm and cytosol

Answer 172

cytosol is just the gel-like substance but cytoplasm is the gel-like substance and everything, including organelles, suspended within

Question 173

what are ribosomes?

Answer 173

site of protein synthesis

made of protein and rRNA

one of the only organelles that are not membrane bound

found in both prokaryotes and eukaryotes

Question 174

what are the 2 subunits of ribosomes in eukaryotes? in prokaryotes? (in S units)

Answer 174

eukaryotes:
60S + 40S = 80S

prokaryotes:
50S + 30S = 70S

the 2 subunits are created in the nucleus and moved to the cytoplasm where they are assembled into a single larger ribosome

s larger S value (Svedberg unit)
indicates a heavier molecule

Question 175

where can you find ribosomes? what can be said about this?

Answer 175

floating in the cytosol or bound to the rough endoplasmic reticulum

ribosomes floating in the cytosol make proteins that function within the cell

ribosomes bound to the ER make proteins that will be exported

Question 176

what is the endoplasmic reticulum?

Answer 176

an extensive network of interconnect membranes with flattened areas called “cisternae”

the ER membrane separates the cytosol from its inner contents, the ER lumen

Question 177

what are the (2) types of endoplasmic reticulum?

Answer 177

rough ER

smooth ER

note that the rough ER is closer to the nucleus

Question 178

describe the rough endoplasmic reticulum. what does it make? what should you note about rough ER in eukaryotes?

Answer 178

the ER is covered in ribosomes

creates glycoproteins by attaching polysaccharides to polypeptides as they are assembled by ribosomes

— in eukaryotes, the rough ER is continuous with the outer nucleus membrane

Question 179

what is the process that occurs with proteins in the ER lumen? describe it

Answer 179

post translational modification

when ribosomes on the rough ER synthesize proteins, they’re injected into the lumen where it can be modified and prepared for transportation

can add groups like carbohydrates/phosphates to proteins!!

Question 180

describe the smooth endoplasmic reticulum. what does it make? what unique function does it have in liver cell?

Answer 180

not covered in ribosomes, hence “smooth”

synthesizes lipids and steroid hormones for export

in liver cells, it break down toxins, drugs, and toxic by-products from cellular reactions

Question 181

what is the sarcoplasmic reticulum?

Answer 181

smooth ER found in smooth and striated muscle

it stores and releases ions like Ca2+

Question 182

where do proteins go after being synthesized?

Answer 182

golgi apparatus

Question 183

what is the golgi?

Answer 183

aids in the transport of various substances in vesicles

helps sort, modify, and transport proteins

a series of flattened membrane sacs called cisternae

also creates lysosomes and transports lipids

Question 184

what are lysosomes?

Answer 184

vesicles produced from the golgi

they contain digestive enzymes with low pH, function in apoptosis (by releasing their contents), and break down nutrients, bacteria, pathogens, and cell debris.

they can also partake in autophagy which is where they fuse with damaged organelles to break them down and recycle

Question 185

how do lysosomes break down nutrients?

Answer 185

when a cell ingests food materials, the cell forms a food vacuole which the lysosome fuses with to break down its contents into useful nutrients

Question 186

differentiate between the faces of the golgi

Answer 186

cis face: for incoming vesicles

trans face: for secretory vesicles

the cis face is more “bent” than the trans face

the cis face is closer to the endoplasmic reticulum

Question 187

what are the steps the golgi takes in transporting and processing substances?

Answer 187

proteins are made by the rough ER or steroid hormones are made by the smooth ER

they’re packaged into vesicles and then sent to the golgi apparatus on the cis face where they can be further packaged and modified

transported in vesicles from the trans face to various parts of the cell or outside the cell

Question 188

what happens to enzymes that escapes from the lysosome?

Answer 188

they remain inactive in the neutral pH of the cytosol

Question 189

what are peroxiosomes? where are they found? what do they do (and in plant cells and in germinating seeds)?

Answer 189

found in the liver and kidney

break down substances, fatty acids, and amino acids. can also inactivate toxic substances

they produce hydrogen peroxide, H2O2, which they use to oxidize substrates, and can also break down H2O2 if necessary (H2O2 → H2O + O2) using the enzyme catalase

in plant cells, peroxisomes modify
by-products of photorespiration.

in germinating seeds, peroxisomes are
called glyoxysomes that break down
stored fatty acids to help generate
energy for growth

Question 190

what are microtubules? what are they made up of? what do they do? where can they be found?

Answer 190

hollow tubes formed from polymers of the protein, tubulin

provides support and movement for cellular activities

act as spindle apparatus, guiding chromosomes during cell division

bundles of microtubules make up other cellular structures like: flagella and cilia of all animal cells and lower plants like
mosses and ferns. and in centrioles

Question 191

describe intracellular transport

Answer 191

microtubules help support motility within the cell. they provide tracks along which organelles and vesicles are transported using motor proteins (kinesin and dynein)

kinesin is a motor protein that binds to the cargo it’s transporting on one end and the other end moves along the microtubule. moves from the center to the periphery (outer area of the cell, where the cell membrane is)

dynein. also binds to cargo on one end and moves with the other end. moves from periphery to center

Question 192

what are cilia?

Answer 192

hair-like projections from a cell

made of microtubules

allows the cell to move. for cells that are in a fixed position (e.g. in the respiratory tract, the cilia move the debris that’s trapped in the mucus out of the airway), cilia move substances in the environment across the cell surface

Question 193

what are centrioles?

Answer 193

are MTOCs (microtubule organizing centers), a structure that microtubules emerge from

2 centrioles, perpendicular to another, make up a centrosome

allows for development of spindle fibers of the spindle apparatus during cell division

they do not have a membrane

Question 194

which organelles are not bound by a membrane?

Answer 194

ribosomes

centrioles

centrosomes

cytoskeleton

(FROM GOOGLE, UNSURE ACCURACY AND IF THERE’S MORE)

Question 195

what are microvilli?

Answer 195

projections from the cell membrane composed of actin filaments that support the microvilli and maintain its shape

function to increase the surface area of the cell which leads to enhance absorption and secretion

commonly seen in cells of the digestive system

Question 196

what is the arrangement of microtubules in flagella and cilia of all animal cells and lower plants like mosses and ferns?

Answer 196

in a 9+2 array - 9 pairs of microtubules with 2 singlets in the center

Question 197

what are intermediate filaments?

Answer 197

provide physical support and stability for maintaining cell shape (e.g. keratin)

Question 198

what are microfilaments?

Answer 198

made of actin

involved in cell movement

found in skeletal muscle, amoeba pseudopod, and cleavage furrows

Question 199

what are microtubule organizing centers (MTOCs)? give 3 examples!

Answer 199

a structure that microtubules emerge from

includes centrosomes (centrioles) and basal bodies

BASAL BODIES: are found at the base of each flagellum and cilium; organization of eukaryotic flagella and cilia and the

CENTROSOMES: organization of the mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division.

plant cells lack centrioles and divide
via cell plates rather than cleavage
furrows — note that plants do have
MTOCs called spindle pole bodies

Question 200

how are microtubule organization centers (MTOCs) arranged?

Answer 200

unlike microtubules, MTOCs are found in a 9x3 array

they are made of 9 triplets of microtubules held together

Question 201

what are transport vacuoles?

Answer 201

moves materials between organelles or organelles and the plasma membrane

Question 202

what are food vacuoles?

Answer 202

temporary containers of nutrients that merge with lysosomes to break down food

Question 203

what are central vacuoles?

Answer 203

found only in plant cells

generally large - can occupy most of the cell wall’s interior

exerts turgor when fully filled (pressure - pushes plasma membrane against cell wall - maintains rigidity)

stores nutrients and water

carries out functions performed by lysosomes in animal cells (degrades material taken up from outside the cell and to digest obsolete components of the cell itself)

Question 204

what’s a tonoplast?

Answer 204

specialized membrane of central vacuoles

Question 205

what are storage vacuoles?

Answer 205

where plants store starch, pigments, and toxic substances such as nicotine

ONLY FOUND IN PLANT CELLS

Question 206

what are contractile vacuoles?

Answer 206

usually found in single-celled Protista organisms like amoeba and paramecium living in hypotonic environments

collects and pumps excess water out of the cell via active transport to prevent bursting

Question 207

what are cell walls?

Answer 207

provides support in plants, fungi, protists, and bacteria

sometimes a secondary cell wall develops beneath the primary cell wall

Question 208

what are cell walls made up (for plants, fungi, bacteria, and archaea - 4)?

Answer 208

plants: cellulose

fungi: chitin

bacteria:
- gram-negative: thin peptidoglycan layer surrounded by lipopolysaccharides attached to an outer membrane above the peptidoglycan layer
- gram positive: thick peptidoglycan layer above one membrane layer (no outer membrane here!)

archaea: polysaccharides

Question 209

what happens when gram-negative bacteria is destroyed?

Answer 209

the lipopolysaccharides are released from the outer membrane as endotoxins, a toxic compound which can trigger an immune response

gram-positive doesn’t have lipopolysaccharides, so no toxins released

Question 210

what is the extracellular matrix?

Answer 210

found in animals between adjacent cells (beyond the plasma membrane and glycocalyx) - provides mechanical support and helps bind adjacent cells

occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by cells

provides structural support (with it’s support proteins); cell adhesion (EM serves as an area of anchorage for cells to attach to); and transmits mechanical and chemical signals between the inside
and outside of the cell

Question 211

describe the network of proteins found in the extracellular matrix that helps bind adjacent cells

Answer 211

collagen and proteoglycans and glycoproteins connected to integrins in the cell membrane via fibronectin

proteoglycan and glycoproteins are proteins that have carbohydrate groups attached. the carbohydrates in glycoproteins are short and branched (used in cell signaling and adhesion), while the carbohydrates in proteoglycan are long and unbranched (used for structural support).

collagen, an incredibly strong protein fiber embedded throughout the EM.

fibronectin attaches proteoglycans, glycoproteins, and collagen to integrin

integrin are proteins located in the cell membrane

by using fibronectin and integrin, cells can anchor themselves to the collagen, proteoglycan, and glycoproteins of the EM, facilitating cell adhesion

Question 212

how do cells adhere/connect to the extra cellular matrix (2)?

Answer 212

focal adhesions (connection of the ECM to actin filaments in the cell) AND

hemidesmosomes (involve the connection of ECM to intermediate filaments like keratin)

Question 213

what are fibroblasts?

Answer 213

cells that produce collagen and other connective tissue elements found in the extracellular matrix

Question 214

what is collagen?

Answer 214

the most abundant protein in mammals

found in bones, muscles, skin, and tendons

fibrous protein present in tissue as triple helix (its structure provides strength)

a repeating pattern of amino acids, every 3rd amino acid is glycine

Question 215

what are plastids? what does it include (6)?

Answer 215

organelles found in plant cells

includes:

chloroplasts (the site of photosynthesis)

leucoplasts: specialized storage of…
- starch [as amyloplasts]
- lipids [as elaioplasts]
- proteins [as proteinoplasts]

chromoplasts (store carotenoids)

Question 216

what are chloroplasts?

Answer 216

double membrane layered organelle

site of photosynthesis (light -> sugar)

has its own circular DNA

most likely descended from a bacteria capable of photosynthesis, cyanobacteria

Question 217

why do chloroplasts appear to be green?

Answer 217

they absorb red and blue wavelengths of light but reflect green

Question 218

describe the structure of mitochondria

Answer 218

double-layered organelle (2 separate phospholipid bilayers)… multiple “layers”: outer mitochondrial membrane, intermembrane space, inner mitochondrial membrane (folded numerous times to increase surface area and ATP production), mitochondrial matrix

Question 219

how does the mitochondria make ATP?

Answer 219

makes ATP thru aerobic cellular respiration

Question 220

what does the endosymbiotic theory state?

Answer 220

states that mitochondria and chloroplasts were once prokaryotic organisms that lived on their own

they were absorbed by a larger cell and formed a symbiotic relationship (larger cell provides protection and they provide energy) with it. eventually they became organelles in eukaryotes

Question 221

what evidence backs the endosymbiotic theory?

Answer 221

mitochondria and chloroplasts have their own genome (circular DNA — eukaryotes have linear DNA and prokaryotes have circular DNA) – also have their own ribosomes

mitochondria and chloroplasts divide by binary fission (they divide independently of the eukaryotic cell they reside in)

contain other structures similar to prokaryotes

Question 222

what is the cytoskeleton? what are the components? where’s it?

Answer 222

helps cells maintain their shape, mechanical support/motility (helps move components within the cell as well), helps anchor/stabilize membrane proteins, and internal organization

includes microtubules (e.g. flagella and cilia), microfilaments, and intermediate filaments

found in eukaryotic cells

aids in cell division, cell crawling, and the movement of cytoplasm and organelles

Question 223

what are microfilaments?

Answer 223

2 intertwined polymer strands of actin

involved in cell motility and other functions

used in skeletal muscle contraction

helps to form the amoeba pseudopod, a projection from a cell that’s used in movement and ingestion

forms the cleavage furrow that’s involved in separating cells at the end of mitosis

Question 224

what are intermediate filaments?

Answer 224

tubes of intertwined coil proteins

the proteins that make up an intermediate filament depends on the type of cell they appear in

e.g. keratin in skin cells

Question 225

describe the behaviour a plant cell undergoes when placed in a hypotonic, isotonic, and hypertonic solution (plant cell and water balance)

Answer 225

hypotonic solution (where there’s less stuff dissolved in water than in the cell): plant cells swell as their central vacuole fill up, making them turgid/firm. fungal cells stay firm in hypotonic conditions due to their cell wall

isotonic solution (where the concentration of dissolved stuff is the same inside and outside the cell): plant cells are flaccid - not swollen and not pushing against the cell wall

hypertonic solution (where there’s more stuff dissolved in water than in the cell): the cell shrinks and pulls away from the cell wall, a process called plasmolysis.

Question 226

describe the behaviour an animal cell undergoes when placed in a hypotonic, isotonic, and hypertonic solution (animal cell and water balance)

Answer 226

hypotonic solution (where there’s less stuff dissolved in water than in the cell): animal cells undergo lysis and burst

isotonic solution (where the concentration of dissolved stuff is the same inside and outside the cell): water moves in and out at equal rates

hypertonic solution (where there’s more stuff dissolved in water than in the cell): water rushes out of the cell, making it shrink - plasmolysis

Question 227

what is the endomembrane system? what does it include?

Answer 227

the network of organelles and structures, either directly or indirectly connected, that help in the transport of proteins and other macromolecules into/out of the cell

includes: plasma membrane, endoplasmic reticulum, golgi apparatus, nuclear envelope, lysosomes, vacuoles, vesicles, and endosomes

does not include: mitochondria and chloroplasts

Question 228

differentiate between the movement of flagella and cilia

Answer 228

flagella: undulates like a snake

cilia: beats in rapid back and forth motions

Question 229

what are the (2) methods of circulation throughout the cell?

Answer 229

intracellular

extracellular

Question 230

describe intracellular circulation

Answer 230

follows brownian movement, the random particle movement due to kinetic energy; spreads small particles throughout the cytoplasm - prevents particles from settling down

the cyclosis (flow/stream of cytoplasm) the circular motion of cytoplasm within the cell

Question 231

what is cyclosis?

Answer 231

movement by the streaming of cytoplasm within a cell. cytoplasm flow is driven by the movement of the cytoskeleton (generated by the contraction and relaxation of actin and myosin filaments)

circulates the cytoplasm around the cell which allows cellular components to be moved around

Question 232

what organelle plays a key role in intracellular circulation? describe the role

Answer 232

endoplasmic reticulum

provides channel through the cytoplasm

provides direct continuous passageway from plasma membrane to nuclear membrane

Question 233

describe extracellular circulation

Answer 233

through diffusion

if cells are close enough to their external environment, diffusion can fulfill food and respiration needs

also used for transport of materials between cells and interstitial fluid around cells in more complex animals

Question 234

what are cell junctions?

Answer 234

protein complexes that connect cells

Question 235

what are the (4) major cell junctions?

Answer 235

anchoring/adhesion

gap

tight

plasmodesmata

Question 236

what are anchoring junctions? list the types (3) and describe them

Answer 236

desmosomes: (keratin intermediate filaments attached to adhesion plaques which bind adjacent cells via adhesion proteins), providing mechanical stability by holding cellular structures together (stronger than adherens)
- present in animal cells with tissue experiencing mechanical stress - including skin epithelial cells and cells in the cervix/uterus

adherens: also attached to actin filaments on the inside of the cell to further stabilize

hemidesmosomes: attach the cell to the extracellular matrix (prevents it from being detached from the surface easily); also attached to intermediate filaments on the inside of the cell. can be found in the epidermis, the skin’s outer layer

Question 237

what are tight junctions? where could they be found?

Answer 237

fully encircles each cell, producing a seal that prevents the passage of materials between cells. made of transmembrane proteins

common to cells lining the digestive tract where materials are required to pass through the cells into the blood – tight junctions prevent materials to escape between the cells. the materials must enter the cells (via diffusion or active transport) to pass through the tissues in animal cells

Question 238

what are gap junctions? where could they be found?

Answer 238

similar to transport proteins; narrow tunnels between animal cells that prevent cytoplasm of each cell from mixing but allows passage of ions and small molecules for effective cell-cell communication

basically channel proteins of two adjacent cells that are closely aligned

tissues like the heart include these to
quickly pass electrical impulses, because ions like sodium can spread directly from one cardiac muscle cell to the next

connexins: gap junction proteins
- basically channel proteins of two adjacent cells that are closely aligned

Question 239

what is the apical side of the cell?

Answer 239

side of the cell facing the external environment or internal cavity (points outwards or outer surface/top side of the cell)

there are no other cells/tissues touching that surface

Question 240

what is the lateral surface of the cell?

Answer 240

sides of the cell in the tissue

touching the cells adjacent to it

Question 241

what is the basal side of the cell?

Answer 241

bottom of the cell

surface of the cell anchored to the underlying connective tissue

Question 242

what are plasmodesmata?

Answer 242

narrow tunnels between plant cells

desmotubule: narrow tube of endoplasmic reticulum: exchanges material through cytoplasm surrounding the desmotubule

gated plant cell wall channels that allow the movement of molecules between cells

Question 243

what are some features we should note about prokaryotes?

Answer 243

no nucleus

no chromatin level organization of DNA. DNA exists as single, circular, naked, and double-stranded

ribosomes are produced like 50S + 30S = 70S

has cell walls made of peptidoglycan but in archaea made of polysaccharides

flagella constructed from flagellum, not microtubules

Question 244

define a hypertonic solution

Answer 244

higher solute concentration

Question 245

define a hypotonic solution

Answer 245

lower solute concentration

Question 246

define a isotonic concentration

Answer 246

equal solute concentration

Question 247

what is bulk flow?

Answer 247

collective movement of substances such as blood in response to a force or pressure

Question 248

what is considered passive transport? (6)

Answer 248

simple diffusion

osmosis

dialysis (diffusion of different solutes across a selectively permeable membrane)

plasmolysis (movement of water out of a cell that results in its collapse)

facilitated diffusion

countercurrent exchange (diffusion by bulk flow in opposite directions such as blood and water in fish gills)

Question 249

differentiate between simple diffusion and facilitated diffusion

Answer 249

simple diffusion: no proteins used

facilitated diffusion: substances move down the concentration gradient with the assistance of transmembrane transport proteins

Question 250

what is a concentration gradient? what role does this play in passive and active transport?

Answer 250

when substance is more concentrated on one side of the permeable membrane

a biological imbalance that’s energetically unfavourable

normally (to seek balance), substances would go down the concentration gradient (from high conc -> to low conc). this is passive transport

active transport is when the substances move against the concentration gradient

Question 251

what is active transport?

Answer 251

movement of molecules against their concentration gradient – requires energy!

usually involves solutes like small ions, amino acids, and monosaccharides

Question 252

what are the (5) types of active transport?

Answer 252

primary active transport

secondary active transport

group translocation

endocytosis: substances bought into a cell by enfolding them with cell membrane

exocytosis: similar to endocytosis, but transportation out of the cell

Question 253

what are the (2) types of secondary active transport?

Answer 253

antiport: exchange

symport: cotransport

Question 254

define primary active transport

Answer 254

energy (ATP) used to directly move against concentration gradient

Question 255

describe receptor-mediated cytosis

Answer 255

a form of pinocytosis in which in which molecules called ligands bind to receptors

first, molecules outside the cell bind to receptors on the cell membrane. once they bind, a protein called clathrin attaches itself to the areas of the membrane that have bound receptors on the inside. these clathrin proteins form a lattice that pulls the membrane inward and creates a vesicle. the clathrin detaches.

Question 256

define secondary active transport

Answer 256

energy indirectly used to move against concentration gradient (usually with an ion moving down its concentration gradient)

using an established electrochemical gradient to move a substance against its concentration gradient

example: if there’s a high conc of sodium outside the cell and high conc of glucose inside the cell. can link the transport of two together so when sodium moves in (favourable), glucose moves in (unfavourable)

the requirement is that one of the two substances must be moving down it’s concentration gradient

Question 257

define group translocation

Answer 257

seen in prokaryotes when the substance
being transported across the membrane is chemically altered in the process –> prevents it from diffusing back out

Question 258

what are the (3) types of endocytosis?

Answer 258

phagocytosis

pinocytosis “cell-drinking”

receptor-mediated cytosis

Question 259

describe phagocytosis

Answer 259

engulfing particles by extending structures like pseudopods. packaged into a vesicle and can be fused/broken down later. this process is common in the immune system where pathogens can be bought into the cell and then fused with organelles like lysosomes to be destroyed. deals with more larger substance than pinocytosis would

Question 260

describe pinocytosis

Answer 260

plasma membrane forms a pocket and pinches off to form a sort of vesicle in the cytoplasm around the extracellular fluid and dissolved material (liquid). a non-selective process, cell doesn’t care what it’s pulling in

Question 261

what is one way we can trigger exocytosis to occur?

Answer 261

increasing concentration of calcium on the inside of the cell

Question 262

what are (2) processes that tend to use exocytosis?

Answer 262

neurons releasing neurotransmitters

endocrine cells releasing certain hormones into the bloodstream

Question 263

differentiate between diffusion and osmosis

Answer 263

in diffusion, SOLUTES move from higher conc to lower conc

in osmosis, SOLVENT (usually water) moves from higher conc to lower conc

Question 264

describe the relationship between basal metabolic rate (BMR) and body size and body weight

Answer 264

BMR overall, increases as size increases

but BMR also actually decreases per kg as size goes up

(an elephant has a higher BMR than a squirrel. but a squirrel would have a higher BMR per kg)

Question 265

describe the relationship between metabolism, temperature, and age

Answer 265

increased temp = increased metabolism

increased age = decreased metabolism

Question 266

what’s kinetic energy? what’s potential energy?

Answer 266

kinetic: associated with anything with motion e.g. a flagella whipping back and forth

potential: found in objects not moving - the object has potential (stored) energy for later use e.g. energy stored within chemical bonds of glucose and glycogen stored in muscles

Question 267

what is the formula for gibbs free energy? describe coupling in regards to it

Answer 267

G = deltaH - temperature(deltaS)
= change in enthalpy - (temperature x change in entropy)

if G is negative, the reaction is spontaneous (exergonic). energy is released

if G is positive, then non-spontaneous (endergonic). energy is absorbed

chemical reactions can be “coupled” together if they share intermediates. in this case, the overall Gibbs Free Energy change is the sum of the △G values for each reaction.

E.G. an unfavorable reaction with a positive △G1 value can be driven by a second, highly favorable reaction (negative △G2 value where the magnitude of △G2 > magnitude of △G1).

this principle of coupling reactions to alter the change in Gibbs Free Energy is the basic principle behind all enzymatic action in biological organisms, and is how ATP drives chemical work.

Question 268

what is one of the most favourable reactions we can use to drive non-spontaneous reactions?

Answer 268

the breakdown of ATP, an exergonic reaction releasing energy

the bonds between the close together, negative phosphate groups of ATP release significant amount of energy when they’re broken via hydrolysis

NOTE: the formation of ATP from the oxidative phosphorylation of ADP is endergonic, requiring energy

Question 269

what is metabolism? what are the (2) different pathways?

Answer 269

sum of all chemical reactions taking place

categorized into catabolic (energy releasing) and anabolic (energy consuming) pathways

provides the reactions necessary to produce the energy every cell needs

metabolism = catabolism + anabolism + energy transfer

Question 270

what are the laws of thermodynamics?

Answer 270

1: energy can’t be created or destroyed - only transferred and transformed

2: the transfer of energy leads to an increase of entropy over time (for closed systems! – doesn’t apply to organisms that are living systems. our entropy decreases over time at the expense of the environment)

3: as a system approaches absolute zero temperature (0K), entropy approaches a minimum

Question 271

how do catalysts lower the activation energy?

Answer 271

stabilize the transition state

provide an alternate pathway with a lower activation energy for the reaction

Question 272

how do substrates bind to enzymes?

Answer 272

bind via induced fit: the structure of the enzyme’s active site changes in response to the enzyme binding to it. the tighter fit brings the chemical groups of the substrate closer together, creating a more favourable environment for the reaction

a series of weak interactions NOT strong covalent bonds

Question 273

how do enzymes work?

Answer 273

a substrate binds to the active site of an enzyme and is held in place by temporary (non-covalent) bonds

while the substrate is bound to the active site, the enzyme catalyzes its conversion into a product molecule

the product molecule is released from the active site and a new substrate will bind

Question 274

what are zymogens?

Answer 274

aka proenzymes

inactive precursor to enzymes; once cleaved, they’re able to function

e.g. pepsinogen –(low pH)–> pepsin

Question 275

how can enzyme regulation take place? (3)

Answer 275

at the genetic level: genes that produce enzymes can be activated or disabled depending on the needs of the cell

at the physical level: enzymes can be stored in vesicles (contents released when cell requires their activity)

at the enzyme level:
- proenzymes (zymogens) can be cleaved to activate them
- can be activated/disabled via chemical modification (e.g. phosphorylation)
- can be modified by having another molecule bind to them, altering their level of activity

Question 276

what is feedback inhibition (negative feedback)?

Answer 276

when the product of a reaction binds to one of the earlier enzymes in its metabolic pathway, inhibiting its activity

the enzyme will no longer function and the product will stop being produced

most enzymes are regulated by this type of feedback (prevents too much product from being formed) and it’s how the body maintains homeostasis

Question 277

what is positive feedback?

Answer 277

a product of the enzyme triggers more product formation – creating a loop that increases in magnitude over time

e.g. labor contractions during birth (oxytocin production)

Question 278

briefly describe cellular respiration and state the formula

Answer 278

cellular respiration is the overall oxidative/combustion, exergonic process (spontaneous) that breaks down (catabolic) glucose in order to derive energy in the form of ATP

considered oxidative because glucose is ultimately losing electrons which are used to make ATP

C6H12O6 + 6(O2) ——> 6(CO2) + 6(H2O) + energy (heat and ATP)

during respiration, high energy H atoms are removed from organic molecules (dehydrogenation)

Question 279

in what 2 forms does cellular respiration produce energy?

Answer 279

heat and ATP

Question 280

how is mitochondrial DNA inherited?

Answer 280

exclusively from your mother, since her eggs provides all the mitochondria to the growing embryo

Question 281

where can the mitochondria’s DNA and ribosomes be found?

Answer 281

in the mitochondrial matrix

Question 282

define substrate level phosphorylation and oxidative phosphorylation

Answer 282

substrate level phosphorylation: production of ATP using enzyme catalyzed reactions. direct transfer of phosphate groups to ADP

oxidative phosphorylation: ATP produced using energy from redox reactions of the ETC

Question 283

what is external and internal respiration?

Answer 283

external respiration: entry of air into the lungs and subsequent gas exchange between alveoli and blood

internal respiration: exchange of gas between blood and the cells.

Question 284

what (4) major steps make up cellular respiration?

Answer 284

glycolysis

pyruvate decarboxylation (links glycolysis and krebs cycle) (once for each pyruvate)

krebs cycle

electron transport chain

Question 285

what is glycolysis? where does it take place?

Answer 285

decomposition of glucose into pyruvate in the cytosol

the purpose is to produce pyruvate (which will be used in the citric acid cycle) and ATP

takes place in the cytosol

Question 286

describe the formula of glycolysis

Answer 286

glucose + 2NAD + 2ADP -> 2 pyruvate + 2ATP + 2NADH + 2H2O

reactants: glucose, NAD, ADP`
products: pyruvate, ATP, NADH, and water

it takes the 6-carbon glucose and produces 3 2-carbon pyruvate

Question 287

which step of cellular respiration produces the most ATP?

Answer 287

electron transport chain (ETC)

Question 288

describe the (2) important steps of glycolysis

Answer 288

using ATP, hexokinase phosphorylates glucose to glucose 6-phosphate, which is important as this step is irreversible because glucose can’t diffuse out of the cell due to the negative charge it now has. since it can’t leave, it can be immediately usable for energy

LATER IN THE PROCESS,

phosphofructokinase (PFK), using ATP, adds a 2nd phosphate, to convert fructose 6-phosphate to fructose 1,6-bisphosphate, which is irreversible and commits the glucose to glycolysis. this is the rate limiting step

Question 289

is glycolysis aerobic or anaerobic?

Answer 289

glycolysis can occur under both conditions as it does not require oxygen, thus, ANEROBIC

Question 290

how is ATP produced in glycolysis?

Answer 290

ATP is produced via substrate level phosphorylation, which involves the direct transfer of a phosphate group via enzyme, to ADP (no extraneous carriers needed)

the energy for ATP formation comes from the coupled reaction

Question 291

what is the importance of phosphofructokinase adding a 2nd phosphate to fructose 6-phosphate, converting it to fructose 1,6-bisphosphate? how does phosphofructokinase regulate glycolysis?

Answer 291

commits the glucose to glycolysis

the PFK step of glycolysis is the major
regulatory point of glycolysis and is a point of allosteric regulation that controls the overall rate of glycolysis

an example of negative feedback. when ATP in the cell is high, phosphofructokinase is inhibited and prevents glycolysis from moving forward. when ATP is low, phosphofructokinase is used in abundance, and the cell is free to use glycolysis to make more ATP

it is also the rate limiting step of glycolysis

Question 292

describe the steps of pyruvate decarboxylation

Answer 292

pyruvate becomes acetyl CoA, while
producing 1 NADH and 1 CO2
(net: 2 NADH and 2 CO2 since 2
pyruvate formed in glycolysis)

reaction is catalyzed by PDC enzyme
(pyruvate dehydrogenase complex)

Question 293

where does pyruvate decarboxylation take place?

Answer 293

mitochondrial matrix

but in prokaryotes, it takes place in the cytoplasm

Question 294

describe krebs cycle (fate of pyruvate that is produced in glycolysis) and its steps

Answer 294

in the krebs cycle, acetyl CoA merges
with oxaloacetate to form citrate, and
the cycle continues with 7 intermediates

3 NADH, 1 FADH2, 1 ATP (via substrate
level phosphorylation) and 2 CO2 are
produced per pyruvate molecule. Each
glucose molecule forms two pyruvate in
glycolysis, so the cycle turns two times,
creating a net of 6 NADH, 2 FADH2, 2
ATP (technically GTP), and 4 CO2. The CO2 produced here is the CO2 animals exhale during breathing

Question 295

where does the krebs cycle take place?

Answer 295

mitochondrial matrix

but it takes place in the cytosol for prokaryotes

Question 296

where does the electron transport chain (ETC) take place?

Answer 296

in the inner membrane/cristae of the mitochondria (the folds increase surface area for more ETC action)

ETC is embedded into the membrane and the membrane can host multiple so more space = more ETC = more ATP produced

in prokaryotes, this process takes place in the cellular membrane

Question 297

what are the (2) other names for krebs cycle?

Answer 297

citric acid cycle

tricarboxylic acid cycle

Question 298

what is aerobic respiration?

Answer 298

aerobic pathway of cellular respiration

organic compounds and oxygen react in a combustion reaction that produces energy

Question 299

why are muscle cells abundant in mitochondria?

Answer 299

mitochondria are responsible for synthesizing very large amounts of ATP for cells to survive. the higher energy needs of a cell are, the more mitochondria it will have

since muscle cells (like cardiac and skeletal) require lots of energy to move, they will have many mitochondria.

Question 300

what is the purpose of pyruvate decarboxylation?

Answer 300

to synthesize acetyl-CoA

Question 301

how is ATP produced in the citric acid cycle?

Answer 301

ATP is produced via substrate level phosphorylation, which involves the direct transfer of a phosphate group via enzyme, to ADP (no extraneous carriers needed)

Question 302

describe the important steps of the citric acid cycle?

Answer 302

first, acetyl-CoA merges with oxalacetate forming citrate

this citrate will go thru multiple steps, progressively being turned into different intermediates. during this process, electrons are stripped away and used to form different products

at the end, oxalacetate is reformed and the cycle can repeat

NOTE: this cycle happened twice per glucose!! 1 glucose -> 2 pyruvates -> 2 acetyl CoA

Question 303

what is produced in the citric acid cycle?

Answer 303

NAD, ATP, FADH2, CO2

note that we technically get 2 acetyl-CoA from glucose so this cycle happens twice

Question 304

where does the CO2 that animals exhale come from?

Answer 304

citric acid cycle

Question 305

what is the purpose of NADH and FADH2?

Answer 305

coenzyme nucleotide molecules that function as high energy electron carriers

during glycolysis and the citric acid cycle, electrons are removed from glucose and transferred, converting NAD+ and FAD to NADH and FADH2. these electrons are eventually used to create ATP in the ETC

Question 306

what is the electron transport chain?

Answer 306

a series of proteins embedded in the inner membrane of the mitochondria

IN ANAEROBIC CELLULAR RESPIRATION, the electron transport chain is found in the cellular membrane

in this process, the proteins pass high energy electrons through the chain, ultimately allowing the production of ATP

Question 307

what are the steps of the electron transport chain (ETC)?

Answer 307

NOTE: this is oxidative phosphorylation

first, NADH and FADH2 ferry electrons to the ETC and drop them off (converting back to NAD+ and FAD – they are oxidized!! – and go back to glycolysis/CAC to repeat their process) to other electron carriers/proteins

as electrons pass through the proteins of ETC, protons (H+ ions) are pumped across the inner mitochondrial membrane and into the intermembrane space, establishing an electrochemical gradient. the intermembrane space has a high proton concentration (high pH - acidic) while the mitochondrial matrix has a low proton concentration

note that as the electrons move through, they slowly lose energy due to the pumping of protons. the movement of electrons throughout the ETC is a highly exergonic reaction which is coupled with the endergonic pumping of protons against the gradient

in the final step of the ETC, electrons are transferred from a protein to oxygen gas (O2). which then combines with hydrogen ions in the mitochondrial matrix to form water. oxygen is the final electron acceptor, NOT water. water is the final PRODUCT

ATP synthase forms ATP from ADP via oxidative phosphorylation (powered by the series of redox reactions from the acceptance and transfer of electrons). the build up of protons (H+ ions) in the intermembrane space goes against the desired balance. the protons wish to even out and move down the electrochemical gradient into the mitochondrial matrix (chemiosmosis). these protons move down through ATP synthase which uses the flow of protons (proton motive force) to create ATP from ADP – like using wind for energy!

Question 308

between NADH and FADH2, which has more energy? when is this seen?

Answer 308

NADH has more energy than FADH2 and is able to “pump” more protons across the membrane. NADH pumps 3 protons for every 2 protons FADH2 pumps.

Question 309

in the ETC, how are protons able to be continuously pumped against the concentration gradient?

Answer 309

the movement of electrons throughout the ETC is a highly exergonic reaction which is coupled with the endergonic pumping of protons against the gradient

note that as the electrons move through, they slowly lose energy due to the pumping of protons

Question 310

what is the final electron acceptor in the ETC?

Answer 310

in the final step, electrons are transferred from a protein to oxygen gas (O2). which then combines with hydrogen ions in the mitochondrial matrix to form water. oxygen is the final electron acceptor, NOT water

water is the final PRODUCT

Question 311

what is proton motive force?

Answer 311

promotes movement of protons across membranes downhill the electrochemical potential – providing energy that can be used to power other reactions OR

its energy can either be used right away to do work, like power flagella, or be stored for later in ATP

Question 312

what is chemiosmosis?

Answer 312

movement of ions across a selectively permeable membrane, down their electrochemical gradient

Question 313

what is the total yield for 1 glucose molecule going through aerobic cellular respiration? why is there a discrepancy in numbers of the total of all the individual processes of respiration and the actual total?

Answer 313

glycolysis: 2 ATP & 2 NADH

• 2ATP for NADH to be transported into the cytosol

pyruvate decarboxylation: 2 NADH

citric acid cycle: 2 ATP & 6 NADH & 2 FADH2

electron transport chain: 34 ATP

total: 36 ATP (38 - 2)

Question 314

how is ATP produced in the electron transport chain? describe the steps

Answer 314

via oxidative phosphorylation, series of redox reactions where electrons are transferred and accepted etcc

ATP synthase forms ATP from ADP via oxidative phosphorylation (powered by the series of redox reactions from the acceptance and transfer of electrons). the build up of protons (H+ ions) in the intermembrane space goes against the desired balance. the protons wish to even out and move down the electrochemical gradient into the mitochondrial matrix (chemiosmosis). these protons move down through ATP synthase which uses the flow of protons (proton motive force) to create ATP from ADP – like using wind for energy!

Question 315

what’s the key difference between aerobic and anaerobic cellular respiration?

Answer 315

in anaerobic respiration, the last electron acceptor is not oxygen!

some alternatives: SO4, NO3, S, etc. – as long as it’s not oxygen

Question 316

what is fermentation? how’s it different from respiration?

Answer 316

anaerobic process that isn’t respiration. there’s no citric acid cycle or ETC

fermentation allows for the regeneration of NAD+ without needing CAC or ETC. this is done thru the partial breakdown of glucose. note that, respiration is the complete breakdown of glucose

Question 317

what are the steps of alcohol fermentation?

Answer 317

this is after glycolysis turns glucose into 2 pyruvate molecules

pyruvate is converted to acetaldehyde and CO2

acetaldehyde and NADH (from glycolysis) is converted to ethanol and NAD+

acetaldehyde acts as the final electron acceptor, becoming ethanol. ethanol is the final product

the NAD+ is replenished, allowing more glycolysis to take place

note that these fermentation steps do not produce any ATP

Question 318

which organisms generally partake in alcohol fermentation?

Answer 318

yeast and some bacteria

Question 319

what are the steps of lactic fermentation?

Answer 319

this is after glycolysis turns glucose into 2 pyruvate molecules

pyruvate and NADH is converted to lactate and NAD+

the NAD+ is replenished, allowing more glycolysis to take place

note that these fermentation steps do not produce any ATP

Question 320

which organisms generally partake in lactic fermentation?

Answer 320

human muscle cells, fungi, bacteria

Question 321

what happens to lactate in humans following lactic fermentation?

Answer 321

the lactate is transported from the muscle cells to the liver where it’s converted back to glucose via the cori cycle. the glucose is sent back to the muscle cells to use as energy

Question 322

out of all human cells, why does lactic fermentation occur in muscle cells?

Answer 322

muscles turn to this process when we we have low oxygen availability due to physical exertion - to continue generating ATP

Question 323

what are the two types of fermentation?

Answer 323

alcohol and lactic

Question 324

where does fermentation occur?

Answer 324

in the cytosol – where glycolysis takes place

Question 325

why do prokaryotes ultimately gain more ATP from aerobic respiration than eukaryotes? what’s the ATP difference?

Answer 325

NADH does not need to be transported into the mitochondrial matrix for prokaryotes

the transportation of NADH requires the consumption of 2 ATP. note that pyruvate doesn’t require ATP to be transported as its symport with protons

so, prokaryotes gain 38 ATP and eukaryotes gain 36 ATP

Question 326

what other macromolecules can be used as an energy source when glucose has been used up?

Answer 326

other carbohydrates

lipids

proteins (lowk a last resort)

Question 327

what is glycogenesis? describe how it works

Answer 327

occurs when we have more than the necessary amt of glucose

glucose monomers are linked together to form the polymer, glycogen

–

first, an ATP is used to turn glucose to glucose-6-phosphate. then a bunch of other steps…

lastly, we have our branched polymer of glycogen

Question 328

where can glycogen be found?

Answer 328

generally in the liver and in skeletal muscles as they can store large amounts. but technically all cells can store glycogen

stored for later use

Question 329

how are other carbohydrates like fructose and galactose used in metabolism?

Answer 329

they are converted to glucose-6-phosphate which can then be used in glycolysis and other metabolic pathways such as glycogenesis

Question 330

what is glycogenolysis?

Answer 330

occurs when we are lacking in glucose

glycogen is broken down into glucose-6-phosphate which can be used in glycolysis

Question 331

what is gluconeogenesis?

Answer 331

when other biological macromolecules such as lipids and proteins are converted into glucose

AKA conversion of non-carbohydrate precursors into glucose

Question 332

where does gluconeogenesis mainly occur?

Answer 332

liver and kidneys

remember that gluconeogenesis is the conversion of non-carbohydrate precursors into glucose

Question 333

how is carbohydrate metabolism regulated?

Answer 333

via two hormones produced by the pancreas: insulin and glucagon

Question 334

what role does insulin play in carbohydrate metabolism?

Answer 334

insulin is released when blood glucose levels are too high.

what insulin does:
- cells will uptake glucose and make use of the glucose, producing ATP (promotes glycolysis). insulin activates the phosphofructokinase enzyme to promote glycolysis

• excess glucose made into glycogen (promotes glycogenesis)

Question 335

what role does glucagon play in carbohydrate metabolism?

Answer 335

glucagon is released when blood glucose levels are too low

what glucagon does:
- glycogen is broken down into glucose for energy (promotes glycogenolysis)
- inhibits glycogenesis (to produce energy) and glycolysis (to conserve energy). it inhibits the phosphofructokinase enzyme to inhibit glycolysis

note that glycolysis is only inhibited in certain organs so organs that actually need it more have energy (like the brain)

Question 336

how are proteins able to be used for energy?

Answer 336

proteins are broken into amino acids which are then converted in various molecules that can enter the citric acid cycle at various points, such as acetyl-CoA, pyruvate, oxaloacetate (depends on the amino acid)

first, remove the amino group from the amino acid through a process called deamination. this amino group will now exists as ammonia which is then converted into urea (more harmless than ammonia which is toxic when accumulated)

Question 337

what is the purpose of breaking down nucleic acids?

Answer 337

different components can be “salvaged” to form new nucleotides and certain parts can be excreted in urea

Question 338

how does a lipid, such as triglyceride able to be used for energy?

Answer 338

note that triglyceride is a glycerol carbon backbone connected to 3 fatty acid chains

first, the triglyceride must be broken down into its components. the enzyme lipase splits apart the glycerol backbone and fatty acids

the glycerol is phosphorylated to G3P, an intermediate is glycolysis. it enters the glycolysis cycle like this

fatty acids in the blood combine with the protein, albumin which carries them throughout the bloodstream. in the mitochondrial matrix, fatty acids are broken down for energy in a process called beta-oxidation. every time we break down a fatty acid, we take two of its carbons and combine it with another molecule to form acetyl-CoA. with each acetyl-CoA we produce, we also get 1 NADH and 1 FADH2 (-1 FADH2 per double bond from the total). this process repeats! we can get lots of ATP this way but note that 1ATP is used for activation of the fatty acid chain

Question 339

what is beta oxidation? where does it take place?

Answer 339

fatty acids are broken down for energy in a process called beta-oxidation. every time we break down a fatty acid, we take two of its carbons and combine it with another molecule to form acetyl-CoA. with each acetyl-CoA we produce, we also get 1 NADH and 1 FADH2 (-1 FADH2 per double bond from the total). this process repeats! we can get lots of ATP this way but note that 1ATP is used for activation of the fatty acid chain

takes place in the mitochondrial matrix of eukaryotes and cytosol of prokaryotes

Question 340

what does the brain use for energy when there’s no glucose?

Answer 340

ketones, a byproduct from the breakdown of fatty acids in the liver

these ketones can enter the citric acid cycle where they will produce ATP

Question 341

how many calories do fats and carbohydrates and proteins store? what does this mean?

Answer 341

fats are 9 calories/gram, whereas carbohydrates and proteins are 4 calories/gram

fats store more energy than carbohydrates
per carbon - their carbons are in a more
reduced state – this explains the amount of calories for the macromolecules

Question 342

briefly describe photosynthesis and state the formula

Answer 342

captures energy from sunlight and converts it into chemical energy – organisms that partake in this process are called photoautotrophs

plants take in CO2 and water and convert it into glucose and O2

6(CO2) + 6(H2O) ——> C6H12O6 + 6(O2)

Question 343

what are chloroplasts?

Answer 343

photosynthesis takes place in chloroplasts which is found in plants and photosynthetic protists/bacteria

it contains a molecule called chlorophyll (found in proteins called photosystems embedded in the thylakoid membrane) that captures energy from sunlight and uses it the energy to make glucose from water and CO2

Question 344

describe the structure of chloroplasts

Answer 344

outer membrane

intermembrane space

inner membrane

stroma: similar to the cytoplasm of cells. where all of the internal structures of the chloroplast are suspended in

stroma lamellae: connects thylakoid

thylakoid: membrane bound structures that look like flattened discs. the inside is called thylakoid lumen (some parts of photosynthesis take place in here). stacked thylakoids are called granum

Question 345

what’s chlorophyll? how does it capture energy from sunlight?

Answer 345

embedded in the photosystems of the thylakoid membrane in chloroplasts.

chlorophyll contains a porphyrin ring centered around Mg

it captures energy from sunlight and uses it the energy to make glucose from water and CO2

photons from the sunlight hit electrons in the chlorophyll molecule and excites the electrons to a higher state which begins the photosynthesis process

Question 346

what are the (2) sets of reactions that make up photosynthesis?

Answer 346

light dependent reactions: cyclic and non-cyclic photophosphorylation

light independent (dark) reactions aka calvin cycle: doesn’t require photons

Question 347

what are the (2) important photosystems of light dependent reactions? what are their other names? briefly describe the two different photosystems and what they produce

Answer 347

photosystem I - 680nm

photosystem II - 700nm

their second set of names comes from the approximate wavelengths they absorb

photosystem II captures energy and starts the process of high energy electron transfer. primarily used to generate ATP

photosystem I gets electrons after they’ve been passed through photosystem II. it boosts them with energy again to eventually produce NADPH

Question 348

describe the steps in the process of non-cyclic photophosphorylation (a light dependent reaction)

Answer 348

the photons from the sunlight excite the electrons (gained through photolysis) found in photosystem II, boosting them to a higher energy level

excited electrons passed to primary electron acceptor

primary electron acceptor will pass electron through the electron transport chain (ETC)

as the electron is passed, the energy from this process is used to pumps protons (H+ ions) from the stroma into the thylakoid lumen, against the concentration gradient. this establishes an electrochemical gradient

ATP synthase catalyzes the reaction of ADP to ATP using the flow of protons going down the gradient (proton motive force/chemiosmosis). note that 3 H+ ions produce 1ATP

the electrons that passed through the ETC arrive at photosystem I in a low energy state as it’s energy was used up as it moved from acceptors and moving protons against the gradient. photons hit photosystem I, exciting the electrons. the electron is passed to an acceptor at the start of another ETC.

as the electrons travels down the ETC, it combines with a molecule called NADP+ and H+ (from photolysis), forming NADPH

Question 349

in the non-cyclic photophosphorylation, how much ATP is produced per 2 electrons going down the ETC?

Answer 349

2 electrons phosphorylate 1.5 ATP

Question 350

in the cyclic photophosphorylation, how much ATP is produced per 2 electrons going down the ETC?

Answer 350

1 ATP

Question 351

what is the purpose of the light dependent reactions of photosynthesis?

Answer 351

non-cyclic photophosphorylation produces:

ATP to be used in the light independent (dark) reactions and NADPH that will help power the formation of glucose in the dark reactions.

cyclic photophosphorylation produces:

more ATP (dark reactions require more ATP than NADPH)

Question 352

what is the overall formula of the light dependent reactions of photosynthesis?

Answer 352

H2O + ADP + Pi + (NADP+) + light →

ATP + NADPH + O2 + (H+)

Question 353

what is the overall formula of the light independent reactions of photosynthesis?

Answer 353

6CO2 + 18ATP + 12NADPH →

18ADP + 18 Pi + 12(NADP+) + 1 glucose (or 2 G3P)

Question 354

what’s photolysis? what’s the purpose of it?

Answer 354

the splitting of water by light during photosynthesis. water splits into hydrogen ions, electrons, and oxygen. the hydrogen ions are used in the concentration gradient, the electrons are stored in the photosystems to be used in the light dependent reaction, and the oxygen is given off by plants into the atmosphere (what we breathe in)

occurs in the thylakoid lumen

Question 355

where does photolysis occur?

Answer 355

thylakoid lumen

Question 356

where does non-cyclic photophosphorylation, a light dependent reaction occur?

Answer 356

thylakoid lumen, it passes electrons to the thylakoid membrane

Question 357

where does cyclic photophosphorylation, a light dependent reaction occur?

Answer 357

stroma lamellae

Question 358

describe the steps in the process of cyclic photophosphorylation (a light dependent reaction)

Answer 358

note that only photosystem I is used in this process

–

REMEMBER THAT photosystem I gets its electrons from the ETC that feeds into it (direction of photosystem II)…. photons from sunlight excite the electrons residing in photosystem I

the electrons then get passed back to the
(beginning of??) ETC that pumped H+ ions across the membrane until it’s back at photosystem I, while also pumping H+ ions across

repeats

Question 359

where does the calvin cycle take place?

Answer 359

in the stroma

Question 360

what is the purpose of the calvin cycle of photosynthesis?

Answer 360

to convert CO2 into glucose

Question 361

what’s carbon fixation?

Answer 361

taking carbon from an inorganic source and converting it into an organic compound

e.g. taking CO2 from the atmosphere and converting it into glucose in the calvin cycle

Question 362

what (3) phases make up the calvin cycle?

Answer 362

carbon fixation: in this situation, carbon from CO2 is used to produce an organic compound

reduction: using the ATP and NADPH generated from the light dependent reactions

regeneration: recycling intermediates to regenerate RuBisCo, an enzyme

Question 363

what is the most abundant enzyme on earth?

Answer 363

RuBisCO – essential for carbon fixation

Question 364

describe the steps in the calvin cycle

Answer 364

enzyme, RuBisCo combines CO2 and ribulose biphosphate (RuBP) forming an organic compound — this is carbon fixation!!

the 6-carbon compound we formed into 2 phosphoglycerate (PGA)

using ATP and NADPH, the PGA molecules are phosphorylated into G3P. the now ADP and NADP+ go into non-cyclic photophosphorylation

some G3P is converted back to the ribulose bi-phosphate (to allow the calvin cycle to continue again) and some G3P is converted to glucose

in order to make ONE molecule of glucose, we need to calvin cycle to occur 6 times. out of the 12 G3P produced, 10 is used to reform ribulose biphosphate and 2 used to form glucose

Question 365

what are the products of the calvin cycle?

Answer 365

glucose and regeneration of ribulose biphosphate

in order to make ONE molecule of glucose, we need to calvin cycle to occur 6 times. out of the 12 G3P produced, 10 is used to reform ribulose biphosphate and 2 used to form glucose

Question 366

what is photorespiration?

Answer 366

when O2 is used instead of CO2 in the calvin cycle, producing a useless byproduct, a 2-carbon molecule (photosynthesis produces 3-carbon molecules). this byproduct can be broken down by peroxisomes

O2 competitively inhibits RuBisCo

Question 367

what can competitively inhibit RuBisCo?

Answer 367

oxygen!

both O2 and CO2 can bind to RuBisCo

CO2 is preferred, O2 is not!

CO2 leads to calvin cycle

O2 leads to photorespiration

Question 368

what are the types of photosynthesis? what plants partake in each?

Answer 368

C2 = photorespiration - an “accidental” process; all plants

C3 = normal photosynthesis; all plants

———- different versions of photosynthesis that prevents/mitigates certain problems

C4: mitigates photorespiration by spatial separation; corn and sugarcane

CAM: mitigates water loss by temporal separation; cactus and pineapple (found in locations with higher temps)

Question 369

what is C4 photosynthesis?

Answer 369

it prevents photorespiration by physical separation of the light and dark reactions of photosynthesis

NOTE THAT IN C3 RESPIRATION, THE CALVIN CYCLE OCCURS IN THE MESOPHYLL CELLS. in C4 respiration, RuBisCo is found in the bundle sheath cell, so the calvin cycle only occurs there

oxygen can’t reach the bundle sheath cells, thus, unable to competitively inhibit RuBisCo

only occurs in plants that follow Kranz anatomy. has the following layers from outside to inside: mesophyll cells, bundle sheath cells, vascular tissue (veins)

Question 370

describe the steps of C4 photosynthesis

Answer 370

first, PEP carboxylase combines CO2 with PEP (instead of RuBP), forming oxalacetate (a 4-carbon compound) which is then converted to malate. this occurs in a mesophyll cell (one of the outer cells).

the malate is then moved to a bundle sheath cell (a layer deeper). the malate is converted into 2 products: CO2 and pyruvate

the pyruvate is shuttled back to the mesophyll cell and converted back to PEP

the CO2 in the bundle sheath cell undergoes the calvin cycle to produce glucose

glucose can be shuttled to the vascular tissue for transport for plant cells that need it

Question 371

what’s the main drawback of C4 photosynthesis?

Answer 371

the use of extra ATP to pump 4C compounds (malate) to bundle sheath cells

Question 372

what’s the hatch and slack pathway?

Answer 372

aka the C4 photosynthesis pathway

explains that little presence of oxygen reduces competition while RuBisCo is deciding to fix either carbon dioxide or oxygen

Question 373

what is CAM (crassulacean acid
metabolism) photosynthesis? why does this process exist (explain the problem this tries to prevent)?

Answer 373

prevents water loss from plants by temporal separation (day and night)

plants have stomata, pores found on the bottom of leaves, that serve as the site of gas exchange. it’s how CO2 enters and O2 leaves. usually, the stomata are always open to allow the plant to continuously take in CO2 to produce glucose. BUT, if these are open, water can also leave the plant through the stomata.

in CAM photosynthesis, the stomata is open at night and closed during the day.

Question 374

describe the steps in the process of CAM photosynthesis

Answer 374

in CAM photosynthesis, the stomata is open at night and closed during the day

so at night, CO2 enters. rather than going through the calvin cycle right away (we can’t bc no sunlight!!), PEP carboxylase combines CO2 with PEP, forming maleic acid.

the maleic acid is then stores in the plant cell’s vacuole for later. when it’s daytime, the plant closes the stomata to prevent water loss (especially during higher temperatures)

the plant moves maleic acid out of its storage and converts it back into malate and then CO2 and PEP with the use of 1ATP.

the CO2 then goes through the calvin cycle to produce glucose.

Question 375

what’s the role of carotenoids in photosynthesis?

Answer 375

main function is to absorb light energy in the blue-green and green regions of the electromagnetic spectrum that chlorophyll cannot absorb effectively. allows carotenoids to broaden the range of light wavelengths that can be utilized for photosynthesis.

carotenoids also help protect the plant from damage caused by excessive light energy. acts as antioxidants, neutralizing harmful free radicals produced during photosynthesis. helps prevent damage to the plant’s cells and tissues.

Question 376

what results in the orangeness seen in leaves as they age?

Answer 376

as leaves age, chlorophyll breaks down to
extract valuable components like Mg2+,
and carotenoids become visible

Question 377

what (2) processes make up cell division?

Answer 377

nuclear division: dividing the genetic material and nucleus

cytokinesis: dividing the cytoplasm (happens near the end of anaphase)

Question 378

where on sister chromatids linked together?

Answer 378

in a constricted region called the centromere

Question 379

how many chromosomes are in a human diploid? haploid

Answer 379

diploid: 46

haploid: 23

Question 380

what are homologous chromosomes?

Answer 380

a pair of chromosomes that are similar in length, gene position, and centromere position. carry genetic information for the same shape but are not identical

one inherited from the mother, and one from the father

humans have 23 pairs but in a male, the X and Y sex chromosomes are technically not considered to be homologous

Question 381

what’s miotic spindle?

Answer 381

full set of spindle fibers during cell division

the spindles attach to the chromosomes and separates them

Question 382

how do spindle fibers attach to the chromosomes?

Answer 382

they attach to the protein, kinetochore, which adheres to the centromere

the kinetochore serves as an anchor point for spindle fibers, allowing them to change the position of the chromosomes during cell division

Question 383

what are the (5) different phases of mitosis? just list them

Answer 383

prophase

prometaphase

metaphase

anaphase

telophase

cytokinesis, a separate process also occurs around the end of anaphase

Question 384

what are the (5) different phases of mitosis? describe what happens during each

Answer 384

prophase
- chromatin condenses into chromosomes
- nucleolus disappears (where ribosomes are made) – nucleus still intact
- miotic spindles begin to form as the centrosomes it emerges from are slowly pushed to opposite ends

prometaphase
- nuclear membrane breaks down and disappears
- chromosomes condense further
- kinetochore proteins are attached to each chromatid
- miotic spindle fiber continues to develop, some of it has even attached to the kinetochores

metaphase
- chromosomes are lined up across the middle of the cell – “metaphase plate”
- centrosomes have reached opposite ends of the cell
- miotic spindle is fully developed and fibers are attached to all chromosomes via kinetochores

anaphase - shortest step of mitosis
- begins when miotic spindle begin to shorten, pulling the sister chromatids apart. each chromosome pulled to opposite end of the cell (important to note, once the sister chromatids are separate, each chromatid is considered a chromosome)

telophase (cytokinesis, a separate process also occurs around the end of anaphase)
- nucleolus redevelops and 2 new nuclear membranes develop
- chromosomes decondense into chromatin
- spindle fibers disassemble

Question 385

what happens during prophase and prometaphase of mitosis?

Answer 385

PROPHASE

chromatin condenses into chromosomes

nucleolus disappears (where ribosomes are made) – nucleus still intact

miotic spindles begin to form as the centrosomes it emerges from are slowly pushed to opposite ends

PROMETAPHASE

nuclear membrane breaks down and disappears

chromosomes condense further

kinetochore proteins are attached to each chromatid

miotic spindle fiber continues to develop, some of it has even attached to the kinetochores

Question 386

what happens during metaphase of mitosis?

Answer 386

chromosomes are lined up across the middle of the cell – “metaphase plate”

centrosomes have reached opposite ends of the cell

miotic spindle is fully developed and fibers are attached to all chromosomes via kinetochores

Question 387

what happens during anaphase of mitosis?

Answer 387

begins when miotic spindle begin to shorten, pulling the sister chromatids apart. each chromosome pulled to opposite end of the cell (important to note, once the sister chromatids are separate, each chromatid is considered a chromosome)

this is the shortest step of mitosis

Question 388

what happens during telophase of mitosis?

Answer 388

nucleolus redevelops and 2 new nuclear membranes develop

chromosomes decondense into chromatin

spindle fibers disassemble

Question 389

differentiate between cytokinesis in an animal and plant cell

Answer 389

animal cell
- a structure called a cleavage furrow forms. it’s a contractile ring made of actin and myosin filaments
- the ring gradually tightens and gets smaller, pinching the cell into two separate cells - the actin and myosin filaments are shortening

plant cell
- a structure called a cell plate (made of vesicles from golgi bodies) forms in the middle. it extends and fuses with the cell wall, separating the cell into two cells

Question 390

when karyotyping be performed during mitosis?

Answer 390

during metaphase

considered to be the most convenient time as chromosomes are fully developed and lined up, making them easy to separate

Question 391

what are the (8) different phases of meiosis? describe what happens during each

Answer 391

prophase I
- nucleolus and nucleus disassembles
- chromatin condenses into chromosomes
- meiotic spindle begins to form and centrosomes begin to move towards opposite ends
- homologous chromosomes pair up (synapsis). they sit on top of each other in a structure called tetrad. crossing over occurs at the chiasmata (where they swap segments)
- microtubules from the meiotic spindle begin to attach to the kinetochores of the homologous chromosomes

metaphase I
- paired homologous chromosomes are lined up across the metaphase plate (independent assortment)
- kinetochores of chromosome are attached to microtubules emerging from the meiotic spindle

anaphase I
- homologous chromosomes within the tetrads will uncouple and be pulled apart to opposite sides of the cell in a process called disjunction
- note that sister chromatids are still paired together in their chromosomes

telophase I
- nuclear envelope redevelops
- chromosomes decondense
- each nucleus will have half the number of chromosomes that we started out with so we now have 2 haploids (note that the chromosomes are still in their duplicated state and not separated!!)

depending on the species, interphase may occur here in between meiosis I and meiosis II

prophase II
- nucleus and nucleolus disassembles
- chromosomes condense
- meiotic spindle develops and starts to attach to the chromosomes

metaphase II
- chromosomes line up across the metaphase plate
- meiotic spindle has fully formed and is attached to every chromosome at the kinetochore
- note that we have half the number of chromosomes than we did in metaphase I and that the sister chromatids are no longer identical to one another due to crossing over

anaphase II
- microtubules of the meiotic spindle shortens and the sister chromatids of each chromosome are pulled apart to opposite ends of the cell. as soon as they are apart, each chromatid is now considered a chromosome

telophase II
- nucleolus and nucleus reforms
- chromosomes decondense back into chromatin
- spindle fibers disappear

Question 392

what’s the synaptonemal complex?

Answer 392

protein structure that temporarily forms
between homologous chromosomes; gives rise to tetrad with chiasmata and crossing over

Question 393

differentiate between quiescent and senescent

Answer 393

quiescent is reversible in the G0 phase of the cell cycle

senescent is permanently in the G0 phase of the cell cycle

Question 394

what happens during prophase I of meiosis?

Answer 394

nucleolus and nucleus disassembles

chromatin condenses into chromosomes

meiotic spindle begins to form and centrosomes begin to move towards opposite ends

homologous chromosomes pair up. they sit on top of each other in a structure called tetras. crossing over occurs at the chiasmata (where they swap segments)

microtubules from the meiotic spindle begin to attach to the kinetochores of the homologous chromosomes

Question 395

what happens during metaphase I of meiosis?

Answer 395

paired homologous chromosomes are lined up across the metaphase plate (independent assortment)

kinetochores of chromosome are attached to microtubules emerging from the meiotic spindle

Question 396

what happens during anaphase I of meiosis?

Answer 396

homologous chromosomes within the tetrads will uncouple and be pulled apart to opposite sides of the cell in a process called disjunction

note that sister chromatids are still paired together in their chromosomes

Question 397

what’s disjunction?

Answer 397

homologous chromosomes within the tetrads will uncouple and be pulled apart to opposite sides of the cell

during anaphase

Question 398

what happens during telophase I of meiosis?

Answer 398

nuclear envelope redevelops

chromosomes decondense

each nucleus will have half the number of chromosomes that we started out with so we now have 2 haploids (note that the chromosomes are still in their duplicated state and not separated!!)

Question 399

what happens during prophase II of meiosis?

Answer 399

nucleus and nucleolus disassembles

chromosomes condense

meiotic spindle develops and starts to attach to the chromosomes

Question 400

what happens during metaphase II of meiosis?

Answer 400

chromosomes line up across the metaphase plate

meiotic spindle has fully formed and is attached to every chromosome at the kinetochore

note that we have half the number of chromosomes than we did in metaphase I and that the sister chromatids are no longer identical to one another due to crossing over

Question 401

what happens during anaphase II of meiosis?

Answer 401

microtubules of the meiotic spindle shortens and the sister chromatids of each chromosome are pulled apart to opposite ends of the cell. as soon as they are apart, each chromatid is now considered a chromosome

Question 402

what happens during telophase II of meiosis?

Answer 402

nucleolus and nucleus reforms

chromosomes decondense back into chromatin

spindle fibers disappear

Question 403

how does meiosis give rise to genetic diversity? (3)

Answer 403

crossing over (during prophase I)
- creates unique chromosomes that aren’t identical to the parents they come from

independent assortment (during metaphase I)
- the mix of which chromosomes in a homologous pair gets separated to which end of the cell is random

random joining of gametes
- the combination of which sperm fertilizes which egg
- NOTE: joining of gametes is random, but some sperm cells contain genetic material that gives them a competitive advantage - so they all aren’t “equally” competitive

Question 404

what’s the interphase?

Answer 404

sequence of events that occurs before the cell undergoes cell division

this is where cells spend the majority of their time

Question 405

what are the (3) separate phases of the cell’s interphase? what happens during these phases?

Answer 405

G1: cell grows in size. increases protein synthesis to prepare for cell division (e.g. DNA polymerase used in S) - most cell growth is here

S (synthesis): duplicates genetic material, forming sister chromatids. also duplicates centrosomes. cell also grows here

G2: cell continues to grow in size and synthesizing proteins. the cell will also replicate its organelles during this phase. cell checks to see if mitosis can proceed

Question 406

what’s G 0? (the phase outside of the cell cycle)

Answer 406

“resting phase”

cells are still active and functional. they aren’t dividing or preparing to divide

nerve cells and muscle cells are often found in this phase

Question 407

differentiate between quiescent or senescent

Answer 407

quiescent is temporarily in the G0 phase and can reenter the cell cycle when they need to divide.

senescent is permanently in the G0 phase due to damage or degradation.

Question 408

why do our cells divide instead of just growing bigger?

Answer 408

there are functional limitations to what a cell can do when it passes a certain size due to the

• surface to volume ratio
• genome to volume ratio

Question 409

why is the surface to volume ratio important for a cell’s function?

Answer 409

a smaller surface to volume ration (when the cell becomes bigger in size) leads to difficulties in cellular exchange

a large cell has a large volume which means it needs tons of nutrients and oxygen, so it needs a larger surface area to be able to facilitate its needs

this also applies to getting rid of waste

Question 410

why is the genome to volume ratio important for a cell’s function?

Answer 410

as a cell grows larger in volume, the genome amount doesn’t change.

our genome is used to express genes and produce proteins. the larger a cell is, the more processes that need to be regulated

Question 411

what are some exceptions to the genome/surface to volume ratio rule of cells?

Answer 411

skeletal muscles remain in the G0 phase and don’t divide. they’re even capable of growing larger with exercise. the skeletal muscle cells don’t follow this limitation bc

• they have multiple nuclei (large genome to volume ratio)
• long and cylindrical (large surface area to volume ratio)

Question 412

what are the (5) ways in which the cell cycle can be regulated?

Answer 412

cell cycle checkpoints: to make sure the cell is ready to divide

density dependent inhibition: stops cells from dividing when overcrowded

anchorage dependence: makes sure cells are firmly attached to a surface to be able to divide — so a cell that comes loose and is traveling thru your lymphatic vessel or thru your blood can’t divide

cyclin-dependent kinases (CDK’s): a CDK enzyme activates proteins that regulate the cell cycle via phosphorylation. CDK’s are activated by protein cyclins, which vary in type and concentration throughout each phase of the cell cycle

growth factors: a secreted biologically active molecule that can affect the growth of cells. definition has become expanded to include secreted molecules that promote or inhibit mitosis or affect cellular differentiation. the plasma membrane contains receptors for growth factors

note that cancer cells can “defy” the last 4 methods of regulation

Question 413

when are the (3) regulation checkpoints in the cycle? what do they check for?

Answer 413

end of G1 phase (before the cell enters S) aka restriction checkpoint

makes sure the cell is ready to replicate it’s DNA by checking:
- if the cell has proper nutrients to go thru cell division
- if it has necessary cell products to replicate its DNA
- if the cell has grown sufficiently large and if its DNA is intact and error-free and undamaged

end of G2 phase (before the cell enters mitosis)

checks to see if the DNA replicated properly: DNA has been duplicated and that the DNA is error-free and undamaged

if there’s any issues, the cell can pause here and make any repairs necessary or finish the DNA duplication

metaphase (mitosis) aka M checkpoint aka spindle checkpoint

checks that each of the sister chromatids is attached to a spindle fiber, if so, anaphase is triggered. if not attached, mitosis halts until all are chromosomes are properly attached to spindle fibers

Question 414

what happens if the cell fails one of the cell cycle checkpoints?

Answer 414

the cell can either permanently enter the G0 phase and stop dividing or go thru apoptosis (cell death)

Question 415

what happens if there are regulations for cell division?

Answer 415

the cell goes thru uncontrolled cell division eventually leading to cancer

Question 416

describe the development of a cancer cell

Answer 416

a normal cell divides only when it’s supposed to but it can develop mutations that disrupt our ability to regulate cell division, which allows the cell to divide uncontrollably — increasing the amount of mutated cells — leading to large dangerous masses of cells called tumors

Question 417

differentiate between malignant and benign tumors

Answer 417

malignant is when the uncontrollably dividing mutated cells have broken loose and spread to other tissues – this process is called metastasis

benign is localized

Question 418

define metastasis

Answer 418

when the uncontrollably dividing mutated cells have broken loose and spread to other tissues – this is called a malignant tumor

Question 419

what’s p53?

Answer 419

a tumor supressing gene – like Rb

limits cell division –> prevents tumors from forming

if the one of the p53 gene gets mutated, it becomes easier for the cell to divide uncontrollably. if both copies get mutated, the ability to stop cell proliferation has been impaired and cancer is likely to develop

Question 420

what do cancer drugs do?

Answer 420

the main goal is to limit the amount of cell division

many drugs work by inhibiting mitosis directly
e.g. disrupting the ability of miotic spindle to form and disassemble during the cell cycle –further division no longer possible

Question 421

what are the (3) names used to categorize cells based on how they divide?

Answer 421

labile: constantly dividing and replenishing themselves
- e.g. skin cells

quiescent: cell do not divide; but can be stimulated when needed
- e.g. liver cells

fixed/permanent cells: little to no capacity to divide
- e.g. cardiac muscle cells

Question 422

how does fluorescence microscopy, a type of optical microscopy work?

Answer 422

use of a fluorescent marker to tag certain structures. we then shine light to excite the fluorescent probe.

assist in visually locating protein expression within a cell

can be used on living organisms