What is an enzyme's active site?

• A. The region where the substrate binds to the enzyme
• B. The area where the enzyme is destroyed
• C. The region where the product is released
• D. The region where the enzyme moves energy

Answer: (A)

Enzymes have a specific pocket called the active site that matches the shape of the substrate. The substrate binds there, forming an enzyme–substrate complex. This binding positions the substrate so the chemical reaction can occur more easily, lowering the activation energy needed and speeding up the transformation into product. After the reaction happens, the product leaves the active site and the enzyme is ready to catalyze more molecules. The other ideas don’t fit because the active site isn’t where the enzyme is destroyed, and product release happens after the reaction rather than being defined as the site itself; also, there isn’t a separate region that moves energy—the energy changes happen during the reaction inside the active site.