1. Urea cycle Definition  The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions occurring in many animals that produces urea (NH2)2CO from ammonia (NH3) biochemicalureaNHCOammonia biochemicalureaNHCOammonia

2. Function  Organisms that cannot easily and quickly remove ammonia usually have to convert it to some other substance, like urea or uric acid, which are much less toxic. ureauric acidureauric acid  Insufficiency of the urea cycle occurs in some genetic disorders (inborn errors of metabolism), and in liver failure. genetic disordersinborn errors of metabolism liver failuregenetic disordersinborn errors of metabolism liver failure

3. Urea is less toxic than ammonia. Urea is less toxic than ammonia. The Urea Cycle occurs mainly in liver. The Urea Cycle occurs mainly in liver. The 2 nitrogen atoms of urea enter the Urea Cycle as NH 3 (produced mainly via Glutamate Dehydrogenase) and as the amino N of aspartate. The 2 nitrogen atoms of urea enter the Urea Cycle as NH 3 (produced mainly via Glutamate Dehydrogenase) and as the amino N of aspartate. The NH 3 and HCO 3  (carbonyl C) that will be part of urea are incorporated first into carbamoyl phosphate. The NH 3 and HCO 3  (carbonyl C) that will be part of urea are incorporated first into carbamoyl phosphate.

4. Urea cycle  Ammonia is toxic Readily ionises to ammonium ion NH 4 + NH 4 + converted to urea in liver (urea cycle) Urea contains 2 x NH 2 One from NH 4 + One from aspartate Urea excreted in urine

6. Urea Cycle Enzymes in mitochondria: Enzymes in mitochondria: 1. Ornithine Trans- Trans- carbamylase carbamylase Enzymes in cytosol: 2. Arginino- Succinate Succinate Synthase Synthase 3. Arginino- succinase succinase 4. Arginase.

7. BY:  Abdulrhman Mohammed Twhari.  Ebrahim Mohammed Daghriri