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BCH 4053 exam 3 Questions & Verified
Answers, 2025 / 2026.
allosteric regulation by covalent modification - CORRECT ANSWERS phosphorylation of Serine, Threonine, and Tyrosine, mediated by kinases and phosphatases
glycogen phosphorylase (GPase) - CORRECT ANSWERS breaks down glycogen
expressed in muscle
phosphorylated at Ser 14
when GPase is phosphorylated - CORRECT ANSWERS phosphorylase a
GPase is dephosphorylated - CORRECT ANSWERS phosphorylase b
GPase structure and function - CORRECT ANSWERS dimer with two conformations (R/T)
shift to the R state - CORRECT ANSWERS phosphorylation
adding complexity to regulation by phosphorylation - CORRECT ANSWERS a - inhibited by glucose
b- activated by AMP, inhibited by ATP or G6P
going from the T state to the R state
drug discovery - CORRECT ANSWERS starts with a lead compound; natural product like a plant; should have high affinity for target
lead compounds - CORRECT ANSWERS fine tune drugs
- promote tighter binding
- minimize side effects
- modifications - methyl, chloryl, hydroxyl
bioavailability - CORRECT ANSWERS how much drug reaches target; must be easy to administer
roles of hormones (3) - CORRECT ANSWERS maintain homeostasis
released in response to stimuli
regulate cyclical processes
receptors - CORRECT ANSWERS generate second messengers or activate kinase/phosphatase which activate an enzyme cascade
epinephrine and norepinephrine - CORRECT ANSWERS fight or flight response
steroid hormones - CORRECT ANSWERS secreted by gonads and adrenal glands
glucorticoids - CORRECT ANSWERS stimulates glycogen and fat breakdown
mineralcorticoids - CORRECT ANSWERS regulate excretion salt and water by kidneys
water insoluble hormones - CORRECT ANSWERS transported by transcortin; bound intracellularly and spontaneously pass through membrane
growth hormone - CORRECT ANSWERS secreted by pituitary gland; peptide hormones; stimulate growth; binds extracellularly by GH receptor
SH2 domains - CORRECT ANSWERS all sorts of proteins: kinases, phosphatases, G proteins
Some proteins have both SH2 and SH3 - CORRECT ANSWERS SH2 at one end and SH3 at other end
SH3 domains - CORRECT ANSWERS bind proline rich regions, mediate protein/protein interactions
RTK activation - CORRECT ANSWERS sometimes result in activation of G protein
Example of G protein - CORRECT ANSWERS Ras activation by growth factor
Ras- like proteins - CORRECT ANSWERS guanine exchange (GEF) and GTPase activating proteins(GAP)
types of catalytic mechanisms - CORRECT ANSWERS acid base
covalent
metal ion
proximity and orientation effects
preferential binding of transition state
enzyme properties - CORRECT ANSWERS differ in reacton rate, reaction conditions, reaction speficity, and control
active site limits an enzyme's activity to specific substrates
higher rates of reaction, mild conditions
specific - CORRECT ANSWERS H+ or OH transferred
general - CORRECT ANSWERS H+ or OH generated from TS; rate limiting
histidine - CORRECT ANSWERS side chain is 7 so it is a base and acid
geometric complementary - CORRECT ANSWERS substrate binding site on enzyme is complementary to shape of substrate
enzymes are stereospecific - CORRECT ANSWERS highly stereocspecific in chiral substrates and and catalysis- because of chirality of amino acids in enzyme
cofactors - CORRECT ANSWERS chemical teeth for enzymes; can be metal ions
coenzymes - CORRECT ANSWERS organic molecules that are cofactors
NAD+ and NADP+ - CORRECT ANSWERS examples of cosubstrates
an enzyme provides - CORRECT ANSWERS lower energy pathway from substrate to product - does not affect the overall free energy change
reaction coordinate - CORRECT ANSWERS when reactants approach each other along the minimum free energy path
delta G crit - CORRECT ANSWERS free energy of actication - difference between beginning reactants and transition state
second stage - CORRECT ANSWERS withdrawal of e- from rxn center by electrphile
3rd stage of CC - CORRECT ANSWERS elimination of catalyst
metal ions - CORRECT ANSWERS orient substrates for reaction
oxidation-reduction rxns using oxidation state
shield negative charges
carbonic anhydrase - CORRECT ANSWERS has Zn2+ and polarizes h2O so it does not form OH and reacts with CO
proximity and orientation - CORRECT ANSWERS electrostatic catalysis, reduce rotation, right orientation, and bring substa
three key residues for catalysis - catalytic triad - CORRECT ANSWERS asp- 102 orients and polarizes his 57
his -57 - base and acid
ser- 195 - covalent bond with peptide
oxyanion hole - CORRECT ANSWERS tetrahedral intermediate at high energy state; makes hydrogen bonds with enzyme, binding of transition state
low barrier hydrogen bonds - CORRECT ANSWERS short and strong, chymotrysin transitionstate stabilizer
