A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What does substance X represent in this pathway?
A) an allosteric inhibitor
B) a substrate
C) an intermediate
D) the product

Question

Quizplus · Accepted Answer

Substance X is the initial substrate in the metabolic pathway, as it is the starting material that is converted to Y, then to Z, and finally to A through the action of enzymes. The description provided does not characterize X as an inhibitor or an intermediate product, and it is clearly not the final product A.

A Series of Enzymes Catalyze the Reactions in the Metabolic