Describe the effect that boiling had on pepsin

• A. Boiling activates pepsin
• B. Boiling inactivates pepsin
• C. Boiling has no effect
• D. Boiling changes substrate specificity

Answer: (B)

Enzymes rely on their folded 3D shape to form the active site that binds substrate and catalyzes reactions. Boiling disrupts the noncovalent interactions that maintain that structure, leading to denaturation. When pepsin is denatured, its active site is destroyed, so it can no longer catalyze peptide bond hydrolysis. This inactivation is typically irreversible—cooling won’t restore function because the enzyme has lost its proper shape. Boiling does not activate pepsin, nor does it leave its activity unchanged or simply alter substrate specificity in a beneficial way; it just destroys the functional shape needed for activity.