How do competitive inhibitors affect enzyme activity?

• A. They enhance substrate binding to the enzyme
• B. They bind to a site other than the active site
• C. They reduce enzyme activity by binding to the active site
• D. They increase the enzymatic reaction rate

Answer: (C)

Competitive inhibitors reduce enzyme activity by specifically binding to the active site of an enzyme. This binding prevents the substrate from attaching to the active site, thereby effectively blocking the reaction from occurring. When a competitive inhibitor is present, the enzyme's ability to catalyze its reaction is diminished, as the substrate cannot access the active site. However, this effect can be overcome by increasing the concentration of the substrate, since a higher substrate concentration can outcompete the inhibitor for binding to the active site. This is a key characteristic of competitive inhibition, where the inhibitor and substrate are in direct competition for the active site.