What is the function of pepsin and what triggers its activation?

• A. A protease that digests proteins; activated from pepsinogen by stomach acid.
• B. A lipase that digests fats.
• C. A carbohydrase that digests carbohydrates.
• D. A nuclease that digests nucleic acids.

Answer: (A)

Pepsin is the stomach’s protease, meaning its job is to break proteins into smaller pieces. It’s produced and released as an inactive precursor called pepsinogen. Activation happens in the stomach when hydrochloric acid from the stomach lining lowers the pH; this acidic environment triggers pepsinogen to be converted into active pepsin by proteolytic cleavage. Once active, pepsin works best in these very acidic conditions to digest proteins. The other enzymes described in the options—lipase for fats, carbohydrase for carbohydrates, and nuclease for nucleic acids—do not match pepsin’s function or activation.