Practice Questions

The active site is a specific, flexible 3D pocket formed by a few amino acids that binds the substrate and catalyzes its conversion to product via weak interactions.

A prosthetic group is a non-protein unit that is covalently or very tightly bound to an apoenzyme, making it a permanent part of the functional holoenzyme.

The tertiary structure of an enzyme, which dictates the shape of the active site, is stabilized by hydrogen bonds, ionic interactions, hydrophobic interactions, van der Waals forces, and covalent disulfide bonds.

Enzymes are biological catalysts that accelerate reactions by decreasing the activation energy. They do not provide energy, alter the equilibrium constant, or change the free energy change (ΔG) of the overall reaction.

When substrate is in excess, the reaction rate is directly proportional to enzyme concentration because every additional enzyme molecule can contribute to the product formation rate.

The discovery of ribozymes (RNA catalysts) disproved the long-held belief that all enzymes are proteins.

Compartmentalization separates catabolic and anabolic pathways to prevent futile cycles and concentrates reactants to increase reaction efficiency.

A competitive inhibitor competes for the active site, requiring higher substrate concentrations to reach Vmax, thus increasing apparent Km.

High temperatures disrupt non-covalent bonds (e.g., hydrogen bonds) stabilizing protein structure, causing irreversible unfolding (denaturation) and loss of active site shape.

Irreversible inhibitors covalently modify essential residues or cofactors, leading to permanent enzyme inactivation.