Why do conditions like $\mathrm{temperature}$ and $\mathrm{pH}$ affect the rate of an enzyme-catalyzed reaction?

• A. They increase the enzyme's molecular weight, enhancing its activity.
• B. They alter the enzyme's active site, affecting substrate binding.
• C. They provide energy for the reaction, making it spontaneous.
• D. They change the substrate concentration, increasing reaction rate.

Answer: (B)

Verified step by step guidance

1. Understand that enzymes are proteins that catalyze biochemical reactions by lowering the activation energy required for the reaction to proceed.
2. Recognize that the active site of an enzyme is a specific region where the substrate binds, and this site is highly sensitive to environmental conditions such as temperature and pH.
3. Learn that changes in temperature can affect the kinetic energy of molecules, potentially altering the shape of the enzyme's active site and thus its ability to bind substrates effectively.
4. Explore how pH can influence the ionization state of amino acids in the enzyme's active site, which can lead to changes in the enzyme's structure and function, affecting substrate binding.
5. Consider that while temperature and pH do not directly change the enzyme's molecular weight, they can significantly impact the enzyme's conformation and activity, thereby affecting the rate of the enzyme-catalyzed reaction.