Question

the mechanism by which the end product of a metabolic pathway inhibits an enzyme that catalyzes an earlier step in the pathway is most precisely described as...

competitive inhibition.
cooperativity inhibition.
irreversible inhibition.
feedback inhibition.

Explanation:

• Competitive inhibition: Occurs when a molecule competes with the substrate for the active site of an enzyme. This is not related to the end - product of a metabolic pathway inhibiting an earlier - step enzyme.
• Cooperativity inhibition: Cooperativity is a phenomenon in allosteric enzymes where the binding of one substrate molecule affects the binding of subsequent substrate molecules. It is not the same as end - product inhibition.
• Irreversible inhibition: Involves a molecule binding covalently or with a very high affinity to an enzyme, permanently inactivating it. This is not the case for the described mechanism.
• Feedback inhibition: In a metabolic pathway, when the end - product accumulates, it inhibits an enzyme that catalyzes an earlier step in the pathway. This is a regulatory mechanism to control the rate of the metabolic pathway.

Answer:

feedback inhibition.