Lecture 10- Enzyme Kinetics

Lecture 10- Enzyme Kinetics - Midterm Exam 1 Friday 1:10...

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Midterm Exam 1 Friday, Jan 28, 2011 1:10 – 2:00 pm 198 Young (last name begins with “A” - “L”) 176 Everson (last name begins with “M” - “Z”) Exam covers Chapters 2.6 – 2.9 and all of 9 Closed Book and Closed Notes No electronic devices except calculator Practice Midterm on course website At least one assigned homework problem will appear on the exam Review session on Thur Jan 27 th at 7 pm in Rm 1001 Giedt.
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Enzymes and Catalysis (Chapter 10) General principles of enzyme catalysis: Catalysts lower the Gibbs free energy of transition state (G ) and increase both the forward and reverse reaction rates (k exp(- Δ G /RT). Catalysts do NOT change the equilibrium constant ( Δ G°) but rather increase the rate of establishing equilibrium (K eq = k 1 /k -1 ). Catalysts bind to reactant(s) and get released during product formation (i.e. not consumed during reaction). Ch. 10 Homework : 2, 4, 6, 8, 12, 14, 26, 30, 36 No enzyme Enzyme catalyzed hexokinase E + S ES P + E
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RT H R S B e e h T k k o o Δ Δ = Enzyme Stabilizes Transition State Enzymes lower activation energy ( Δ H º‡ ) and increase Δ S º‡ . E + S ES E + P ES EP Transition state is NOT intermediate
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ES ES‡ E + P Chymotrypsin Active Site NH 3 -x-Phe-Met-x-COO - + H 2 O N-x-Phe + Met-x-C Ser195
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Initial rates method: Initial rate (v 0 ) is slope of tangent at time zero. Measure initial rate at several substrate concentrations. 0 0 0 ] [ ] [ S vs dt S d v t = = [S] E + S E + P ES k 1 k -1 k 2 Michaelis-Menten Kinetics [ ] [] ES k dt P d v 2 0 0 = = [ ] 0 2 max E k V = [E] 0 = [ES] + [E] V max ] [ ] [ max 0 S K S V v M + =
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E + S E + P ES k 1 k -1 k 2 Substitute total enzyme concentration into Pre-equilbrium expression: [] [ ] [ ] ES E E + = 0 Substitute Pre-equilibrium expression for [ES] and solve for v 0 : [ ] S K S E ES S + = 0 Pre-equilibrium Approximation ES k dt P d v 2 0 0 = = fast slow [ ] ] [ ] ])[ [ ] ([ 0 1 1 ES S E S E k k K S = = = [ ] [ ] [ ] [ ] S K S V S K S E
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This note was uploaded on 04/06/2011 for the course CHEM 107B taught by Professor Jamesames during the Winter '09 term at UC Davis.

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Lecture 10- Enzyme Kinetics - Midterm Exam 1 Friday 1:10...

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