UPSC Prelims 2007 Q116: Science & Technology – Biology
Production
of which one of the following is a function of the liver?
- (a) Lipase
- (b) Urea
- (c) Mucus
- (d) Hydrochloric acid
Answer: (b) Urea
Explanation
Liver makes urea
| Liver function | Detail |
|---|---|
| Urea formation | Toxic ammonia from protein breakdown is turned into urea via the ornithine (urea) cycle |
| Bile production | Bile emulsifies fats (stored in gall bladder) |
| Glycogen storage | Stores extra glucose as glycogen |
| Detoxification | Breaks down alcohol, drugs, toxins |
Urea is then removed by the kidneys in urine.
Other options — where they are made:
| Substance | Source |
|---|---|
| Lipase | Mainly the pancreas |
| Mucus | Mucous glands of gut and airways |
| HCl | Stomach (oxyntic/parietal cells) |
Answer: (b) Urea.
Why each option is right or wrong
- (a) Incorrect. Lipase is made mainly by the pancreas.
- (b) CORRECT. The liver makes urea through the ornithine cycle.
- (c) Incorrect. Mucus comes from mucous cells of the gut and airways.
- (d) Incorrect. HCl is made by parietal cells of the stomach.
Key point
Liver makes urea (ornithine cycle); kidneys excrete it. Lipase = pancreas; HCl = stomach.
Remember
Urea is made in the liver.
Common mistakes
- Thinking the kidney makes urea — it only filters and removes it.
- Thinking the liver makes lipase because it makes bile for fat digestion.
- Forgetting the name ornithine cycle (Krebs-Henseleit cycle).
Exam tip
Liver MAKES urea; kidney TAKES urea out.
Sources
- NCERT Class XI — Biology, Ch 16 (Digestion) and Ch 19 (Excretory Products)
- NCERT Class X — Science, Ch 5 (Life Processes)