Protein digestion begins in which organ?

• A. Esophagus
• B. Mouth
• C. Stomach
• D. Large intestine

Answer: (C)

Protein digestion begins in the stomach, where an acidic environment and the enzyme pepsin start breaking down proteins. Hydrochloric acid from the stomach walls lower the pH and denature proteins, making them more accessible to enzymes, while pepsin is activated from its inactive form pepsinogen by this acid. Pepsin cleaves peptide bonds in proteins, starting the proteolysis process. The mouth mainly does mechanical processing and some carbohydrate digestion, while the esophagus transports food and the large intestine focuses on absorption and microbial activity, not initial protein breakdown.