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 :
Code :

Question

UnlockIAS · Accepted Answer

Correct — C, Only 3, that is pepsin alone. Of the three proteases listed, only pepsin is actually released into the stomach. The chief cells of the gastric glands secrete it in an inactive form, pepsinogen; the hydrochloric acid poured out by the neighbouring parietal cells drops the gastric pH to roughly 1.5-2 and clips pepsinogen into active pepsin, after which pepsin itself activates more pepsinogen. Pepsin is an endopeptidase: it cuts the interior peptide bonds of a protein and yields shorter chains — proteoses and peptones — rather than free amino acids. Trypsin and chymotrypsin are not gastric at all. Both are made by the acinar cells of the PANCREAS, travel down the pancreatic duct as trypsinogen and chymotrypsinogen, and are switched on in the DUODENUM: enteropeptidase (enterokinase) from the duodenal lining activates trypsin, and trypsin then activates chymotrypsin. So protein digestion begins in the stomach with pepsin and is completed in the small intestine by the pancreatic proteases.

Why the other options are wrong — (a) This picks the two enzymes that are definitely NOT gastric — chymotrypsin and trypsin are both pancreatic zymogens activated in the duodenum — and simultaneously drops pepsin, the one enzyme the stomach really does release. It is wrong on all three counts.  (b) Pepsin belongs, but trypsin does not. Trypsin is secreted by the pancreas as trypsinogen and is activated by enteropeptidase in the duodenum; it also needs the alkaline conditions of the small intestine, and would be useless in the stomach's acid. Adding one wrong name to the right one still loses the mark.  (d) The 'all of the above' trap, and the commonest wrong answer here. All three are genuine protein-digesting enzymes, so a candidate who only checks 'does it digest protein?' ticks everything. The question asks something narrower — where the enzyme is RELEASED — and on that test two of the three fail.

Concept: Protein digestion is a two-stage, two-organ process. In the stomach, an intensely acidic medium and pepsin begin the job by breaking long protein chains into shorter polypeptides. In the small intestine, alkaline pancreatic juice neutralises the acid chyme and delivers trypsin, chymotrypsin and carboxypeptidase, which finish the work; the brush-border peptidases of the intestinal wall release the final amino acids for absorption. Every one of these proteases is secreted as an inactive precursor — a zymogen — and is activated only after it has left the gland, which is how the pancreas and the stomach lining avoid digesting themselves.

State PCS 2025 Q30 — Science & Technology PYQ with Answer

State PCS 2025 Q30 — Science & Technology PYQ with Answer