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Biochemistry

Enzymes and Reaction Rates

12 terms · by ineedtostudy · updated 4 hours ago

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Terms in this set

Enzyme
A biological catalyst that lowers activation energy without being consumed or changing the equilibrium position.
Active site
The pocket where substrate binds and catalysis happens.
Induced fit
The active site changes shape slightly on binding to grip the substrate — the refinement of the older lock-and-key model.
Substrate
The molecule an enzyme acts on.
Competitive inhibitor
Binds the active site and competes with substrate. Raises apparent Km; Vmax is unchanged.
Non-competitive inhibitor
Binds elsewhere and changes the enzyme's shape. Lowers Vmax; Km is unchanged.
Km
The substrate concentration at half-maximal velocity. A low Km means high affinity.
Vmax
The maximum rate, reached when every active site is saturated with substrate.
Cofactor
A non-protein helper an enzyme needs — often a metal ion such as Zn2+ or Mg2+.
Coenzyme
An organic cofactor, frequently vitamin-derived: NAD+, FAD, coenzyme A.
Allosteric regulation
Binding at a site away from the active site turns activity up or down.
Denaturation
Loss of three-dimensional structure from heat or pH, destroying activity. The sequence is unchanged.