If an enzyme loses its shape due to heat, what is likely to happen?

• A. It will become more efficient
• B. It will denature and stop functioning
• C. It will replicate
• D. It will generate energy

Answer: (B)

Enzymes are proteins that need a specific three-dimensional shape to work, with an active site shaped to fit the substrate. Heat can break the weak bonds that hold that shape in place, causing the molecule to unfold or change shape—a process called denaturation. When denatured, the active site no longer fits the substrate, so the enzyme can’t speed up the reaction. So, the enzyme stops functioning. At lower levels of heat, some reversible changes are possible if cooled, but at higher temperatures denaturation is usually irreversible. The other ideas—becoming more efficient, copying itself, or generating energy—don’t describe what happens to an enzyme when heat disrupts its shape.