Practice Questions

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.

A coenzyme acts as a co-substrate; it binds, accepts a chemical group from one substrate, and transfers it to another, being regenerated in the process.

Cofactors are non-protein components (metal ions or coenzymes) required for the activity of many enzymes, distinguishing simple from conjugated enzymes.

Group specificity means an enzyme acts on a family of structurally related substrates (like alcohols) due to shared functional groups.

A mutation in the small number of residues forming the active site would directly abolish enzyme function, unlike mutations in distant structural or surface regions.