Urea cycle takes place in the liver, starting in the mitochondria of hepatocytes, the only place where free ammonia is released.

Why does urea cycle occur only in liver?

Ureagenesis. The urea cycle is partly cytoplasmic and partly mitochondrial. Only the liver possesses all the enzymes required to synthesize urea from ammonia, and this pathway is strictly located in periportal hepatocytes.

How urea formation takes place?

Urea formation takes place in the hepatocytes of the liver and then it is released into the bloodstream. Then the kidney filters that urea containing blood and excrete out urea from the body in urine. The urea cycle is a biochemical reaction that produces urea from ammonia.