Questions: BIO-201 Topic 1: Anatomy, Physiology, Homeostasis, and the Chemistry of Life PRACTICE IT The function of an enzyme is to speed up the rate of a chemical reaction. prevent a chemical reaction from occurring. change the direction of a chemical reaction. stop a chemical reaction once it has started. increase the activation energy of a chemical reaction.

The answer is the first one: speed up the rate of a chemical reaction.

Explanation for each option:

1. Speed up the rate of a chemical reaction: This is correct. Enzymes are biological catalysts that increase the rate of chemical reactions by lowering the activation energy required for the reaction to proceed.
2. Prevent a chemical reaction from occurring: This is incorrect. Enzymes do not prevent reactions; they facilitate them.
3. Change the direction of a chemical reaction: This is incorrect. Enzymes do not change the direction of a reaction; they only speed up the rate at which equilibrium is reached.
4. Stop a chemical reaction once it has started: This is incorrect. Enzymes do not stop reactions; they help them proceed more quickly.
5. Increase the activation energy of a chemical reaction: This is incorrect. Enzymes lower the activation energy, making it easier for the reaction to occur.

Summary: The function of an enzyme is to speed up the rate of a chemical reaction.