Q.The end product of Ornithine cycle is
a. carbon dioxide
b. uric acid
c. urea
d. ammonia

Where the waste comes from, and the three-step process that removes it

Before urine can form, the body first has to detoxify the ammonia released when cells break down amino acids. The liver does this via the ornithine (urea) cycle: ammonia and CO2 combine (via carbamoyl phosphate synthetase) to form carbamoyl phosphate, which condenses with ornithine to form citrulline; citrulline is converted through argininosuccinate and arginine, releasing urea and regenerating ornithine so the cycle can run again. Urea is the main nitrogenous waste that human urine carries away.

Turning blood plasma and this waste into urine then happens through three sequential nephron processes:

1. Glomerular filtration - blood pressure in the glomerulus passively pushes water and small solutes into Bowman's capsule, producing about 180 L of filtrate a day. …