UPSC Prelims 2007 Q117: Science & Technology – Biology
Which of the following is not a digestive enzyme in the human system?
- (a) Trypsin
- (b) Gastrin
- (c) Ptyalin
- (d) Pepsin
Answer: (b) Gastrin
Explanation
Gastrin is a hormone, not an enzyme
| Substance | Type | Source | Job |
|---|---|---|---|
| Gastrin | Hormone | G-cells of stomach | Tells the stomach to release gastric juice (HCl, pepsinogen) |
| Ptyalin (salivary amylase) | Enzyme | Salivary glands | Starch → maltose |
| Pepsin | Enzyme | Stomach | Proteins → peptides |
| Trypsin | Enzyme | Pancreas | Proteins → peptides (in small intestine) |
Other gut hormones: Secretin and CCK (cholecystokinin) from the small intestine; GIP.
Answer: (b) Gastrin.
Why each option is right or wrong
- (a) Incorrect. Trypsin is a protein-digesting enzyme from the pancreas.
- (b) CORRECT. Gastrin is a hormone that stimulates gastric secretion — not a digestive enzyme.
- (c) Incorrect. Ptyalin is salivary amylase — a starch-digesting enzyme.
- (d) Incorrect. Pepsin is a gastric protein-digesting enzyme.
Key point
Gastrin = hormone (stimulates gastric juice). Ptyalin, pepsin, trypsin = enzymes.
Remember
Gastrin is a hormone, not a digestive enzyme.
Common mistakes
- Assuming every gut substance ending in '-in' is an enzyme — gastrin, secretin are hormones.
- Confusing gastrin (hormone) with gastric juice (secretion).
- Forgetting that pepsin is secreted as inactive pepsinogen.
Exam tip
Gut hormones: Gastrin, Secretin, CCK, GIP. Gut enzymes: Ptyalin, Pepsin, Trypsin, Lipase.
Sources
- NCERT Class XI — Biology, Ch 16 (Digestion and Absorption) and Ch 19 (Chemical Coordination)
- NCERT Class X — Science, Ch 6 (Life Processes)