Urea Cycle

Urea Cycle

Urea Cycle.
Answer.

Urea Cycle Definition

The removal of excess ammonia derived from amino acid catabolism is accomplished by the production of urea, which is excreted in the urine.

This cycle is known as urea cycle

Characteristic Features

• It is also known as Krebs-Henseleit cycle
• Urea cycle takes place in the liver, kidney, intestine and brain.
• Urea synthesis does not occur in the brain, kidney or intestine due to absence of some enzmyes
• Urea formation takes place only in the liver
• Urea cycle takes place partly in the mitochondria and partly in the cytoplasm
• One molecule of ammonia and one molecule of carbon dioxide are converted to one molecule of urea in each turn of the cycle and ornithine is regenerated at the end
• Each turn of the urea cycle requires 4 ATP’s.

Importance Of Urea Cycle:

• The major biological role of urea cycle is detoxification of ammonia
• Toxic ammonia is converted to non toxic urea and excreted in the urine
• The normal blood ammonia level is 40 to 70 micrograms %
• Hyperammonemia occurs due to cirrhosis of the liver or genetic defects in urea cycle enzymes.