Question

Ornithine cycle is related with excretion

• A. urea and water
• B. $CO_2$ & $NH_3$
• C. urea and amino adds
• D. urea and $CO_2$

Answer 1

Answer: (D)

urea and $CO_2$

Answer 2

Ornithine cycle removes urea and $CO_2$. Ureotelic animals which excrete urea, synthesize it from ammonia in liver cells. With the help of a number of enzymes and $ATP$, two molecules of ammonia are combined with a molecule of $CO_2$ to form urea. Formation and transformation of three amino adds namely ornithine, citrulline and arginine, one after the other constitute the major steps in this cycle. That is why, it is known as ornithine, arginine or urea cycle. It is also referred as Kreb-Henseleit cycle after the names of its discoverers.