Question

Which statement is true regarding the fate of Ornithine in urea cycle?

• A. Ornithine is regenerated and used in further urea cycles.
• B. Ornithine is degraded into CO${}_2$ and NH${}_2$.
• C. Ornithine is dissolved in blood and keeps in circulation.
• D. Ornithine is mixed with urine and secreted out.

Answer 1

The correct option is A Ornithine is regenerated and used in further urea cycles.

Urea synthesis is a five step cyclic process, with five distinctive enzymes. In the 5th step of urea cycle, arginase enzyme cleaves arginine to yield urea and ornithine. This regenerated ornithine enters mitochondria for its reuse in the urea cycle.

So, the correct answer is 'Ornithine is regenerated and used in further urea cycles'.