Practice Questions

The triad allows histidine to act as a powerful general base catalyst, abstracting a proton from the serine hydroxyl group to make it a nucleophile.

Non-allosteric enzymes follow Michaelis-Menten kinetics, where the plot of V₀ vs. [S] is a rectangular hyperbola: first-order at low [S] and zero-order at high [S].

An enzyme accelerates both forward and reverse reactions equally by lowering activation energy without changing the equilibrium point or free energy.

Carbonic anhydrase is so efficient that the rate-limiting step is the diffusion of the substrate into the active site.

Ligases catalyze the joining of two molecules with the concomitant hydrolysis of a high-energy phosphate bond, such as ATP.

An inactive apoenzyme becomes an active holoenzyme upon binding its required cofactor, a non-covalent, reversible process essential for regulation.

The active site, a 3D cleft formed by folding, provides the unique chemical and physical environment responsible for an enzyme's power and specificity.

Bell-shaped pH-activity profiles often reflect the ionization of catalytic residues that must be in a specific protonation state to function as acid/base catalysts.

In a coupled assay where enzyme Y and its substrates are in excess, the rate of product formation by Y is proportional to the rate at which X provides its substrate.

A non-competitive inhibitor binds to a separate site, forming a non-productive complex that lowers the concentration of functional enzyme, thus reducing Vmax.