lecture 11 - 11-1MCB354Lecture 11Activation...

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Unformatted text preview: 11-1MCB354Lecture 11Activation EnergyEnzyme-Substrate InteractionsEnzyme Kinetics: KmReading in Lehninger:Chapter 6, pp. 186-19711-211-3Relationship between activation energy and reaction rate- Reaction rate governed by [reactant(s)] and a rate constant k- For S -P, rate or velocity of the reaction, V, (representing amount of Sthat reacts per unit time) is expressed by 1st order rate equation V= k[S]- kis a proportionality constant that reflects the probability of reactionunder a given set of conditions (pH, temp)- Where rate depends on [S], 1st order reaction, khas units of time-1(if 1st order reaction has a rate constant kof 0.03 s-1, then ~3% of S will be converted into P in 1 sec)- Where rate depends on of 2 different compounds, or if reaction is between2 molecules of the same compound, reaction is 2nd order,and V= k[S1][S2][- Expression relating magnitude of kto the activation energy:]- Bottom line: relationship between rate constant kand activation energy G isinverse and exponential (so, lower G, higher reaction rate, and vice versa)- Note: catalysts affect reaction rate, not the equilibriumk=kTh e-/11-4ConceptsActive site- a pocket on the enzymelined with residues whose functionalgroups bind the substrateand catalyze its chemical transformationEnzyme-substrate (ES) complex- formed when substrate is bound in active siteBinding energyWhat is the basis for the large and selective rate enhancements?...
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This note was uploaded on 01/29/2012 for the course MCB 354 taught by Professor Spees during the Spring '09 term at University of Illinois, Urbana Champaign.

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lecture 11 - 11-1MCB354Lecture 11Activation...

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