Which organ contains pepsin to digest proteins?

• A. Mouth
• B. Pancreas
• C. Stomach
• D. Liver

Answer: (C)

Protein digestion in the stomach is driven by pepsin, a protease that functions best in acidic conditions. Pepsin is produced as pepsinogen by chief cells and is activated to pepsin by the acidic environment created by hydrochloric acid from parietal cells. This combination—an enzyme that cleaves peptide bonds and a strongly acidic pH—starts breaking proteins into smaller pieces right in the stomach.

In the mouth, the primary role is mechanical digestion plus salivary amylase, which digests starch, not proteins. The pancreas releases other digestive enzymes like trypsin and chymotrypsin into the small intestine, but pepsin itself isn’t active there. The liver makes bile for fat digestion, not protein digestion. So the site where pepsin operates to digest proteins is the stomach.