What happens to an enzyme when exposed to high temperature and pH?

• A. The enzyme is denatured
• B. The enzyme becomes more active
• C. The enzyme is unchanged
• D. The enzyme is precipitated

Answer: (A)

Enzymes rely on a specific 3D shape to fit their substrate and catalyze a reaction. High temperature increases molecular motion and can break the weaker bonds that hold the folded structure together, while extreme pH disrupts the charges and ionic bonds that stabilize the shape. When these bonds break or rearrange, the enzyme unfolds or misfolds, causing the active site to change or disappear. This loss of structure means the enzyme can no longer bind substrate effectively, so its function is lost—that is denaturation. Mild heat might briefly increase activity by speeding up collisions, but beyond the optimum it decreases activity and under extreme conditions it irreversibly denatures the enzyme. Precipitation can occur in some cases, but the key idea in this scenario is the disruption of the enzyme’s shape leading to loss of function.