The urea cycle occurs in the liver and involves the conversion of ammonia and carbon dioxide into urea, which is then transported via blood to the kidneys and excreted in urine. Ammonia comes from the breakdown of proteins and amino acids in the gut, liver, and muscles. It is transported around the body bound to glutamine and alanine before entering the urea cycle in the liver. The urea cycle utilizes aspartate and bicarbonate as substrates along with three ATP molecules to synthesize urea and fumarate. The cycle is regulated in the short term by substrate availability and long term by enzyme induction, with the exception of ornithine transcarbamoylase which is encoded on the

2. Urea Cycle
• Urea is the major disposal form of nitrogen
• 90% of the nitrogen containing component of urine
• It takes place in liver
• Urea is transported through blood to kidneys for
excretion in urine.

3. Sources of Ammonia
• From Glutamine
• From bacterial action in intestine
• From amines
• From purines and pyrimidines

4. Transport of Ammonia in
circulation
• Glutamine and alanine
• Glutamine synthetase is abundant in liver , skeletal
muscles, CNS.

5. (NH2)2CO
• Source of nitrogen >>> ammonia + Aspartate
• Source of carbon and oxygen>>> bicarbonate
• Utilization of 1 H2O molecule
• Utilization of 3 ATP molecules
• Products : urea and fumarate

8. Regulation
• Short term >>> substrate availability
• Long term >>> Enzyme induction

9. Ornithine transcarbamoylase
The only x linked
All others >>> autosomal recessive

10. Hyperammonia
• Normal 3-35micromoles/litre
• 1000 micromoles/l

11. ammonia has a direct neurotoxic
effect on the CNS. For example, elevated
concentrations of ammonia in the blood cause
the symptoms of ammonia intoxication, which
include tremors, slurring of speech,
somnolence (drowsiness), vomiting, cerebral
edema, and blurring of vision. At high
concentrations,
ammonia can cause coma and death.

12. There are 2 types
• Acquired>>> liver diseases
• Congenital>>>Enzymic deficiency

13. Let's take a review

15. Thank you 💕