In humans, the principal nitrogenous excretory compound (ie, urea) is synthesized in liver by ornithine cycle. In liver, one molecule of CO2 is activated by biotin and combines with two molecules of NH3 in the presence of carbamyl phosphate synthetase enzyme and 2ATP to form carbamyl phosphate and one molecule of H2O is released. Carbamyl phosphate reacts with ornithine and forms citrulline. Citrulline combines with another molecule of ammonia and form arginine that is broken into urea and ornithine in the presence of an enzyme arginase and water. 2NH3+CO2⟶ Arginase NH2−CO−NH2+H2O urea is eliminated mostly through kidney as nitrogenous excretory product.
The principal nitrogenous excretory compound in humans is synthesised
NEET UG 2010 — Zoology Excretory Products and their Elimination
2010mcqmedium
The principal nitrogenous excretory compound in humans is synthesised
Official previous-year question
Held on 30 Apr 2010 · Verified 9 Jul 2026.
Options
- A
in kidneys but eliminated mostly through liver
- B
in kidneys as well as eliminated by kidneys
- C
in liver and also eliminated by the same through bile
- D
in the liver, but eliminated mostly through kidneys
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