Advanced Placement (AP) Biology Practice Exam

What will happen to enzyme activity if a chemical inhibitor is introduced into the reaction?

1. The enzyme will increase its activity

2. The substrate concentration will decrease

3. The reaction rate will remain unchanged

4. The enzyme activity will decrease

The correct answer is: The enzyme activity will decrease

Introducing a chemical inhibitor into an enzyme-catalyzed reaction generally leads to a decrease in enzyme activity. Enzymes are proteins that facilitate biochemical reactions by binding to substrates at their active sites. When an inhibitor is present, it can bind to the enzyme, either at the active site or elsewhere, preventing the substrate from effectively binding to the enzyme or altering the enzyme's conformation in such a way that it cannot catalyze the reaction efficiently. This decrease in enzyme activity is significant because it reduces the rate at which the enzyme can convert substrate into product, ultimately leading to a slowdown or a halt in the reaction. Depending on the type of inhibitor—competitive, non-competitive, or uncompetitive—the effect on the reaction rate may vary, but the overall result is a negative impact on the enzyme's ability to perform its function. In contrast, the other options suggest alternative outcomes that do not align with the typical behavior of enzymes in the presence of inhibitors. For instance, the notion that enzyme activity would increase is contrary to the established principles of enzymology. Similarly, the suggestion that substrate concentration would decrease as a direct effect of an inhibitor misrepresents the relationship between inhibitors and enzyme function. Finally, asserting that the reaction rate remains unchanged fails to