MCAT Biology Flashcards
Water:
H-bond
Rxns
Major solvent for life
H-bonding: maintains liquid state, facilitates hydrophillic/phobic interactions
Rxns: dehydration/condensation, hydrolysis
Lipids
8 types of molecules
fatty acids
Fatty acids, triacylglycerols, phospholipids, glycolipids, steroids, terpenes, eicosanoids, lipoproteins
FA: carboxylic acid w/ carbon chain (usually even numbered, maximum 24 C’s, saturated/unsaturated), building block for lipids
Triacylglycerols
Phospholipids
Glycolipids
glycerol backbone—3 FAs, fats/oils (adipocytes), store energy, insulation
glycerol backbone–2 FA + 1 phosphate group, amphipathic (polar/nonpolar ends), membranes
glycerol–FAs + carbohydrates, membranes of myelinated cells, amphipathic
Steroids
Terpenes
Eicosanoids
4 rings, vitamin D, cholesterol
vitamin A
20 C, local hormones: blood pressure, body temperature, smooth muscle
Prostaglandins (inhibited by aspirin), thromboxanes, leukotrienes
Lipoproteins
ADD
Peptide bond
R-groups
Structure: 1 - 4, types, tertiary influences
Globular/Structural
NH2-CR-carbonyl-NH-CR-carbonyl-OH
R-group: can be polar/non, basic/acidic
1’ - # and sequence
2’ - local folding, alpha helix, beta sheet
3’ - overall shape, influenced by disulfide bonds (2 cysteines), electrostatics (R ions), H-bond, vanderwalls, HYDROPHOBICS
4’ - multiple chains/subunits, prosthetic groups
tend to have specific complex function vs provide support/structure
glycoproteins, proteoglycans, cytochromes
Protein selective denaturation: urea salt/pH mercaptoethanol organics heat
H-bonds
electrostatics (ions)
disulfides
hydrophobic interactions
denatures everything
Carbohydrates, Cn(H2O)n
types
alpha/beta
glycogen
digestion
hexose,pentose,form rings (anomers at C1):
alpha: anomeric hydroxyl + methoxy on opp
beta: anomeric hydroxyl + methoxy same side
glucose w/ 1-4A and 1-6A chains, storage
Plants: starch = 1-4A, cellulose = 1-4B chain
1-4B animals can’t digest, bacteria can
Nucleotide
components
form,bonds
examples
triphosphate-5 C sugar (ring)-nitrogenous base
nucleoside=5C + base (no triphosphate)
polymers (DNA,RNA): phosphodiester bond
double helix
ATP: adenosine triphosphate
also cyclic AMP, NADH, FADH2
Minerals
what are they, function
dissolved inorganic ions
create electrochemical gradients, assist in transport
structure in matrices (bone)
cofactors in proteins (prosthetic group like heme)
Enzymes
what are they?
how do they work?
effects T, pH, concentrations
globular proteins w/ cofactor = cosubstrate or prosthetic group (gets reverted back by end of reaction) like AT, vitamins, metal ions
increase rxn rate, lower activation energy
bind substrate at active site (specificity)
lock+key vs induced fit
T: increases rate until enzyme denatured
pH: enzyme/rxn occurs in given range
substrate conc: rate plateaus as enzyme is saturated
Enzyme inhibition
irreversible
competitive
non-competitive
bind covalently to enzyme, can be highly toxic: penicillin
bind active site (often resemble substrate) lower Km (not Vmax), increase substrate to overcame effects
bind alternate site, often work on multiple enzymes lower Vmax (not enzyme affinity)
Enzyme regulation
5 types
proteolytic cleavage: zymogen/proenzymes get cut to become irreversibly activated
reversible covalent: phosphorylation (kinase) or other modifier
control proteins: subunits (calmodulin, G-protein) can activate/inhibit
allosterics: cofactors change conformation of enzyme, inhibit/activate
neg/pos feedback loop: products loop back to earlier in pathway to affect enzymes
Enzyme classification
names+function
suffix -ase, contains N, subject to denaturation
kinase (phosphorylates) [hexokinase-glucose]
phosphatase (dephosphorylates)
oxidoreductase
transferase
hydrolase
isomerase
lyase (synthase): cut, add to double bond
ligase (synthetase): addition, requires ATP
Cellular metabolism
anabolic (synthesis), catabolic (breakdown)
- macromolecule to constituents
- constituents to acetyl CoA, pyruvate/metabolites, ATP/NADH/FADH2 (oxidation w/o oxygen)
- w/ oxygen: metabolites to citric acid cycle, oxidative phosphorylation, lots of ATP/NADH/FADH2
- w/o oxygen: NAD+/byproducts are expelled as waste
respiration = energy aquisition, aerobic/anaerobic
Glycolysis
general overview
products, stages, type of energy
Step 1: glucose to 2 pyruvate/ATP/NADH
occurs in cytosol, all living things
6C stage: expends 2 ATP, primes
3C stage: synthesizes 4 (total) ATP when dephosphorylating each (2) molecule (net 2 ATP)
substrate-level phosphorylation: energy is gained by dephosphorylating a high energy compound
phosphorylations: requires energy, ionizes molecule –> polar molecule cannont pass through membranes
Glycolysis
some specifics
Some steps:
(hexokinase: reversible in liver) -> gluc-6-phos
- > gluc-1-phos (can go to liver to form glycogen)
- > fruc-6-phos
- > (irreversible) fruc-1-6-biphos
- > PGAL x2 …..
- > 2 pyruvate
Fermentation
type of respiration
products
Step 2 and 3: anaerobic, no oxygen present
pyruvate -> ethanol (in microorganisms/yeast) or lactic acid (in humans) + NAD+ -> expelled as waste
NADH is oxidized to NAD+, recycled in glycolysis (as coenzyme)
Aerobic respiration
products
location/movement
overall rxn
Step 3: oxygen present
pyruvate, NADH (move to matrix of mitochondrion by facilitated diffusion, through porin)
-> acetyl CoA (enters Krebs/Citic Acid cycle)
Overall: including Krebs and glycolysis, net 36 ATP
gluc + O2 -> CO2 + H2O
Krebs/Citric acid cycle
1 glucose = 2 pyruvate = 2 acetyl CoA = 2 turns of cycle
All catabolism:
FA: carbon chains converted to acetyl CoA, glycerol to PGAL to pyruvic acid
Proteins: deaminated, converted to pyruvic acid or acetyl CoA
Electron transport chain
Oxydative phosphorylation
High energy electrons (from NADH) passed down chain to oxygen (final acceptor - forms H2O)
Energy generated is used to establish proton-motive force (proton gradient) by pumping protons into intermembrane space (has lower pH)
ATP synthase creates ATP:
2-3 ATP from 1 NADH
2 ATP from 1 FADH2
DNA
components
bases
bond
nucelotides w/ 4 bases
adenosine, guanine (3 H-bonds) = purines (two rings)
thymine(uracil), cytosine (3 H-bonds) = pyrimidines
phosphodiester bond: 5’-5C sugar-phosphate-3’
Bases on 1’ Carbon on sugar
double strand w/ complement strands
major/minor grooves in double helix
The gene
Eukaryotes v prokaryotes
Euchromatin vs hetero
genome
code for polypeptides (one), messenger, ribosomal, transfer RNA
multiple copies of genes vs one of each
coding, non-repetitive, active transcription vs tightly packed and inactivated
26,000 - 38,000 genes humans
DNA to RNA to peptides/aminos
Replication
properties
start: replisome
basic process
end
semiconservative, bidirectional
replisome: origin of replication, replication fork, leading lagging strand
helicase unwinds, primase builds primer (10 riboNTs), DNA polymerase reads 3to5, builds 5to3 (pyrophosphate hydrolysis), exonuclease proofreads
lagging strand has SSB tetromeres for stability, DNA polymerase formas okazaki fragments, primers removed, DNA ligase joins them
telomeres: eukaryotes, repeated 6 nucleotides, prevent end erosion, telomerase
