Which of the following enzymes is/are released in stomach for protein digestion?

Question

Which of the following enzymes is/are released in stomach for protein digestion?

1. Chymotrypsin

2. Trypsin

3. Pepsin

Select the correct answer using the code given below:

1. A. Only 1 and 2
2. B. Only 3 (Correct answer)
3. C. Only 2 and 3
4. D. 1, 2 and 3

Correct Answer

Option B — Only 3

Detailed Solution & Explanation

The correct answer is Only 3.

Key Points

• 3. Pepsin ✓ is the protein-digesting enzyme released in the stomach. It is secreted by the chief (peptic) cells of the gastric glands in the inactive form pepsinogen, and is activated by hydrochloric acid secreted by the parietal (oxyntic) cells.
• 1. Chymotrypsin ✗ and 2. Trypsin ✗ are pancreatic enzymes, secreted into the small intestine, not the stomach.
• Only pepsin qualifies, giving option (b).

Additional Information

• Enzymes are secreted as inactive zymogens so that they do not digest the gland that makes them:
  • Pepsinogen → Pepsin (activated by HCl)
  • Trypsinogen → Trypsin (activated by enterokinase from the intestinal mucosa)
  • Chymotrypsinogen → Chymotrypsin (activated by trypsin)
• HCl also kills ingested bacteria and provides the acidic pH of about 1.8-2 at which pepsin works best.
• The stomach also secretes rennin (in infants, for milk protein) and gastric lipase. The mucus layer, aided by prostaglandins, protects the stomach wall from self-digestion.