Question

Ornithine cycle was discovered by
A. Krebs
B. Henseleit
C. Krebs and henseleit
D. Ornithine

Answer 1

Hint: Ornithine cycle is also known as urea cycle. It is a cycle of biochemical reactions which produces urea from ammonia. The urea cycle converts highly toxic ammonia to urea for excretion.

Complete answer:
Ornithine cycle is also called an urea cycle or krebs and henseleit cycle. It is named after the discoverers of the cycle. It was later explained in detail by Ratner and Cohen.

This is seen in ureotelic organisms. This urea cycle was the first metabolic cycle to be developed. This cycle occurs in the liver primarily and in the kidneys to a lesser extent.

Body produces a large amount of ammonia. Ammonia is produced by the amino acid catabolism. Ammonia has to be flushed out of the body as it is toxic in nature. Hence the ammonia is to be converted into a less toxic substance if it is not possible to secrete it in natural form. Here is where the urea cycle comes into play. It converts the ammonia into a less toxic substance i.e urea. This conversion occurs in the liver which is further passed to the kidneys through the bloodstream which ultimately excretes it along with urine from the body. In species like birds and insects the conversion is different. Ammonia converts into uric acid as the excretion has to be in solid form.

Hence, The correct answer is, option (C).

Note: Ornithine or urea cycle is named krebs and henseleit on the names of their discoverers. This is an essential metabolic cycle of the body that occurs in the liver. This was further explained in detail by Ratner and Cohen.