Question

Which of the following is correct about urea cycle ?
(1) Urea cycle takes place in the liver cells
(2) Urea cycle involves the union of two molecules of ammonia and a molecule of carbon dioxide
(3) Urea is produced by enzyme arginase
(4) Three molecules of ammonia enter ornithine cycle

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (A)

Urea cycle or ornithine cycle or Krebs Henseliet cycle removes two waste products $\left( NH _{3}\right.$ and $CO _{2}$ ) from the blood in liver cells. It involves the union of two molecules of ammonia and a molecule of carbon dioxide and synthesis of urea. All the steps of this cycle are enzymatic and can be visualized as:

The enzymes involved in step $1,2,3$ and $4$ respectively are ornithine transcarbanylase, argino succinate synthetase, arginine synthetase and arginase.