Inhibitors prevent enzymes from working properly. Explain how a competitive inhibitor works and how it affects the rate of reaction of the enzyme.

Competitive inhibitor molecules are a similar shape to the substrate that fits into the enzyme's active site. The competitive inhibitor competes with the substrate molecules to fit into and bind to the active site, but since they are not the correct substrate, no reaction can take place. The competitive inhibitors block the active site so that no substrate molecules can enter the enzyme's active site, which slows rate of reaction. The level of inhibition depends on the concentration of substrate- increasing the concentration of substrate relative to the concentration of inhibitor will increase rate of reaction (up to a point), as the substrate has more chance of being able to bind to the active site before the inhibitor.