Question

Urea, creatinine, nitric oxide formed by which amino acid:

• A. Histidine
• B. Glycine
• C. Cysteine
• D. Arginine

Answer 1

The Correct Option is D

To determine which amino acid is involved in the formation of urea, creatinine, and nitric oxide, we can analyze each compound's biosynthesis pathway:

1. Urea: The urea cycle, also known as the ornithine cycle, involves the conversion of ammonia to urea in the liver. Arginine plays a crucial role in this cycle, where it is hydrolyzed by the enzyme arginase to produce urea and ornithine.
2. Creatinine: Creatinine is a breakdown product of creatine phosphate in muscle. Creatine is synthesized in the body from the amino acids glycine, arginine, and methionine. Arginine provides the amidine group in the synthesis of creatine.
3. Nitric Oxide: Nitric oxide is produced from arginine by the action of nitric oxide synthase. Arginine is converted to citrulline, releasing nitric oxide in the process.

Considering these pathways, the amino acid involved in the formation of urea, creatinine, and nitric oxide is Arginine.