Question

Urea synthesis takes place primarily in liver because

• A. $N{H}_3$ and $C{O}_2$ are present in liver only
• B. hormone ADH is found in liver only
• C. enzyme arginase is present in liver only
• D. kidney is smaller than liver

Answer 1

Answer: (C)

Urea synthesis takes place in liver through ornithine cycle. In liver, one molecule of $C{O}_2$ is activated by biotin and combines with two molecules of $N{H}_3$ in the presence of carbamyl phosphate synthetase enzyme and $2$ ATP to form carbamyl phosphate and one molecule of $H_{2}O$ is released. Carbamyl phosphate react with ornithine arid form citrulline that combines with another molecule of $N{H}_3$ and form argininee. Arginme is broken into urea and ornithine in the presence of an enzyme arginase and water.