Question

by lowering the activation energy
factors that affect enzyme activity
how do enzymes speed up chemical reactions?
active site
denature

Explanation:

To determine which box the phrase "By lowering the activation energy" matches, we analyze the context of each box:

• "Factors that affect Enzyme Activity": Focuses on what influences enzyme function (e.g., temperature, pH), not how enzymes speed up reactions.
• "How do enzymes speed up chemical reactions?": Enzymes act as catalysts, and a core mechanism of catalysts is lowering the activation energy of a reaction. This directly answers the question of how enzymes accelerate reactions.
• "Active Site": Refers to the region of an enzyme where substrate binds, not the mechanism of speeding up reactions.
• "Denature": Describes the loss of enzyme structure/function, unrelated to speeding up reactions.

Answer:

B. How do enzymes speed up chemical reactions?