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Unformatted text preview: 14-11 Catalysis
• A catalyst provides an alternative reaction pathway of lower Ea • Catalysts participate in reactions, but do not undergo a permanent change. • Homogeneous catalysis.
– The catalyst is in the same phase as the reactants • Heterogeneous catalysis.
– The catalyst is in a different phase (usually solid). – Reactants from gas or solution phase are adsorbed. – Active sites on the catalytic surface are important. 14-5 Catalysis Catalysis on a Surface Enzymes as Catalysts: Human glyoxalase I Enzyme Catalysis E+S k1 k-1 ES ES → E + P k2 Saturation Kinetics
k1 k-1 ES → E + P
d[ES] dt k2 d[P] dt = k2[ES] = k1[E][S] – k-1[ES] – k2[ES]= 0 k1[E][S] = (k-1+ k2 )[ES] [E] = [E]0 – [ES] k1[S]([E]0 –[ES]) = (k-1+ k2 )[ES] [ES] = k1[E]0 [S] (k-1+ k2 ) + k1[S] Michaelis-Menten Kinetics
d[P] dt d[P] dt d[P] dt = k1k2[E]0 [S] (k-1+ k2 ) + k1[S] = k2[E]0 d[P] dt = k2[E]0 [S] (k-1+ k2 ) + [S] k1 = k2 KM [E]0 [S] d[P] dt = k2[E]0 [S] KM + [S] ...
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