Practice Questions

Enzyme specificity arises from the unique 3D structure of the active site, which contains amino acid R-groups positioned to form interactions only with a specific substrate.

The protein portion alone is the inactive apoenzyme, which requires a non-protein cofactor to form the complete, active holoenzyme.

By lowering the activation energy, enzymes allow a much larger proportion of substrate molecules to reach the transition state at a given temperature, increasing the reaction rate.

Unlike inorganic catalysts, enzymes are highly specific and their activity is finely regulated by cellular mechanisms like allosteric control.

Km is a measure of an enzyme's affinity for its substrate, defined as the substrate concentration at which the reaction rate is one-half of the maximum velocity (Vmax).

At high substrate concentrations, all enzyme active sites are occupied. The reaction velocity reaches a maximum (Vmax), and further substrate addition cannot increase the rate.

The Induced Fit model states the active site is not rigid; substrate binding induces a conformational change that properly positions catalytic groups for optimized catalysis.

A coenzyme is a non-protein organic molecule that binds transiently to an apoenzyme, allowing it to be separated by dialysis, unlike a prosthetic group.

Substrate binding is mediated by multiple weak, non-covalent forces which are reversible, essential for both binding and product release.

Enzymes lower activation energy by providing an alternative reaction pathway where specific R-groups orient and stress substrates, stabilizing the transition state.