BCH 311-EXAM 2 condensed

BCH 311-EXAM 2 condensed - Negative G=favorable...

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Negative ΔG=favorable (spontaneous)-energy released Positive ΔG=unfavorable-energy absorbed AE-energy needed to bring reactants to Trans state, free energy doesn’t change—when reaction favorable, AE is low hydrogen peroxide E catalase……. .E+S ES EP E +P— lock key-similar shape while induced fit—change, then fit Weak bond interactions between E and S=driving force cat. 3 distinct mech: general-acid base, covalent, metal ion catalysis Specific Acid Base=+ ion transfer from H2O or weak acid/base General Acid Base=+ ion transferred by AA side chains-in active site Covalent=covalent bond between E and S—new path lower then uncatal. Metal-ion=in solution/tightly bound E participate ionic interactions between E-bound metals and S=stable----1/3 catalysis require 1+ metals Chymotrypsin-protease-cleavage of peptide bonds- (F,W,Y)—increases cleavage by 10^9 by a covalent acyl-enzyme interaction in 2 phases: 1.)Acylation-peptide cleaved—ester linkage formed in pep. Carb and E 2.) Deacylation-ester link hydrolyzed and nonactulated E regenerated Key Sites: Ser195, His57, D(ASP) 102---S195 strong nucleophile(e- rich) H57 bound to D102=hydrogen bond=catalysis triad —then compressed = low barrier H-bond----H57 acts as base, then covalent catalysis happens, Then H57 acts as base, then H57 acts as acid—pulls in proton 1 st Order-depends on Concentration-----0 Order- doesn’t depend on Concen. Greater value Km, higher affinity for S. Turnover #-# moles of S to react to form product per mole E per unit Time Kcat-# S molecules converted to product in given time on single E Rate Kcat/Km-diffusion control 10^8 to 10^9==catalytic perfection Reversible Inhibitor—substance that binds to E, but can release it 2 types: Competitive: binds to active site+blocks
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BCH 311-EXAM 2 condensed - Negative G=favorable...

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