The diagram represents an allosteric enzyme.

Where would the following inhibitors be most likely to bind?

D

There were some comments from teachers about the clarity of the diagram. More than three quarters of candidates answered it correctly, and in fact all that was needed was the identification of the active site as the position at which a competitive inhibitor would bind. The diagram might be useful in future teaching as it distinguishes between the binding sites of three types of inhibitor: competitive, non-competitive allosteric and non-competitive non-allosteric.