Kinetics of Catalysis Slides and Notes - Kinetics of Catalysis Catalyst speeds up a reaction by increasing Arrhenius factor A or more commonly lowering

Kinetics of Catalysis Slides and Notes - Kinetics of...

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Kinetics of Catalysis Catalyst speeds up a reaction by increasing Arrhenius factor A , or more commonly lowering activation energy E a by providing a new activated complex of lower potential energy. Both forward and reverse reactions sped up by catalyst. Catalyst has no effect on thermodynamics. Inhibitor slows a reaction, often by increasing E a . Useful to prevent undesirable reactions.
Enzyme Catalysis
Enzyme Catalysis Kinetics of enzyme catalysis consistent with following mechanism: E + S k –1 k 1 ES ES k 2 E + P E = free enzyme, S = substrate, ES = enzyme-substrate complex, P = product of reaction. Determine rate of formation of P by steady- state approximation: d [ES] dt = 0 = k 1 [E][S] – k –1 [ES] – k 2 [ES] Solve equation in terms of total enzyme concentration [E] 0 = [E] + [ES]. Replace [E] in above eqn by [E] 0 – [ES]. d [ES] dt = 0 = k 1 [E] 0 [S] – k 1 [ES][S] – k –1 [ES] – k 2 [ES]
Enzyme Catalysis Solve for [ES]: d [ES] dt = 0 = k 1 [E] 0 [S] – k 1 [ES][S] – k –1 [ES] – k 2 [ES] [ES] = k 1 [E] 0 [S] k 1 [S] + k –1 + k 2 ( ) Define K m = k –1 + k 2 k 1 Then [ES] = [E] 0 [S] [S] + K m Rate of formation of product is d [P] dt = k 2 [ES] = k 2 [E] 0 [S] [S] + K m Michaelis-Menton equation
Enzyme Catalysis Rate linear at low [S] but levels off at high concentration. When [S] small, rate increases with increasing substrate conc.

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