We are looking at the difference between allosteric inhibition and competitive inhibition. Both are inhibitory interactions, meaning a chemical will reversibly bind to an enzyme to help stop its mode of action. There are different ways in which the chemical (called an inhibitor) can bind to the enzyme to inhibit it. Competitive inhibition means that both the inhibitor and substrate bind to the enzyme's active site, or the main site of chemical activity on the enzyme. If the inhibitor is bound to the active site then the substrate is unable to bind and the enzyme's activity is inhibited. For allosteric inhibition, the inhibitor binds to a secondary site on the enzyme and causes the active site to change shape and become less active. The main difference between the two is that for competitive both species bind to the active site while for allosteric they both bind to different sites.