Question

Molecule A is the substrate for enzyme X. Which is more likely to be a competitive inhibitor of enzyme X: molecule B or molecule C? Explain.

Short answer

Molecule B is more likely to act as a competitive inhibitor of enzyme X because molecule B is structurally similar to the substrate (molecule A).

Step-by-step solution

Enzymes        

Enzymes are biological protein catalysts that change the rate of a process in a living organism. All the enzymes bear an active site which is the binding region of the substrates (reactant).

Competitive inhibitor

A competitive inhibitor is a chemical substance that competes with the substrate for the active site of the enzyme. Thus, a competitive inhibitor affects the rate of an enzyme-catalyzed reaction.

Molecule B act as a competitive inhibitor for enzyme X

Molecule A is Pyruvic acid.

Molecule B is Acetone.

Molecule C is 4-nitrophenyl acetate.

Molecules A and B are aliphatic, whereas molecule C is aromatic. Moreover, the structure of molecule B is identical to that of molecule A. This is because both molecules have three carbon atoms and a C=O group at the end of the chain.Thus, molecule B will act as a competitive inhibitor of enzyme X.