Practice Questions

The lock-and-key model proposes that the enzyme's active site (lock) is a rigid, pre-shaped template perfectly complementary to a specific substrate (key).

Once all substrate is consumed, adding more enzyme cannot generate more product, and the reaction rate plateaus due to substrate depletion.

Activation of zymogens requires specific, irreversible proteolytic cleavage to remove a blocking peptide, allowing the protein to fold into its active conformation.

Higher temperatures increase molecular kinetic energy, leading to more frequent and forceful collisions that increase the chance of overcoming the activation energy barrier.

Malonate is a structural analog of succinate and competes for the active site of succinate dehydrogenase, demonstrating competitive inhibition.

Allosteric regulation involves binding to a regulatory site, which induces a conformational change transmitted to the active site, modifying its affinity or efficiency.

A competitive inhibitor binds directly to the active site. This inhibition is overcome by high substrate concentrations; Vmax remains unchanged but apparent Km increases.

Ribozymes are biologically active RNA molecules that possess catalytic activity, proving that biocatalysis is not exclusively the domain of proteins.

Km is the substrate concentration at half of Vmax. A low Km indicates high affinity, requiring only a low concentration to reach effective catalytic rates.

Enzyme specificity results from the chemical complementarity between the active site and the substrate's transition state.