Competitive inhibition: effect on Km and Vmax
A researcher adds a reversible inhibitor that binds only to the free enzyme, at the active site. Compared with the uninhibited reaction, which change in kinetic parameters is expected?
Answer A: explanation for every choice
Correct. A competitive inhibitor competes with substrate for the active site. More substrate is needed to reach half-maximal velocity (apparent Km rises), but at saturating [S] substrate outcompetes the inhibitor, so Vmax is still reachable.
This is pure noncompetitive inhibition: the inhibitor binds E and ES equally at an allosteric site, so affinity is unchanged but functional enzyme is lost.
This is uncompetitive inhibition, where the inhibitor binds only the ES complex. The stem says it binds only free enzyme.
No classic reversible inhibitor increases apparent substrate affinity. A lower Km with no Vmax change is the reverse of the correct answer.
Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb1.