Question

At which stage of ornithine cycle arginase is used?

• A. Arginine - Ornithine
• B. Ornithine - Citruline
• C. Fumaric acid - Arginine
• D. Glycolysis - Urea

Answer 1

Answer: (A)

Arginine - Ornithine

The metabolic breakdown of amino acids releases nitrogen that must be converted to a relatively non-toxic form and then excreted. In mammals, the nitrogen is converted to urea in the liver through a series of reactions, called the urea cycle. Urea is released from arginine by the enzyme arginase, bringing the cycle back around to ornithine. Ornithine is the carrier of carbon and nitrogen atoms.

So, the correct answer is option A.