Ornithine cycle/ deamination ( role of liver in protein metabolism)

Proteins are broken down to peptides in stomach and duodenum after which the peptides are broken down finally to amino acids in the ileum.When amino acids are in excess the body, the body does not store them but rather breaks them down in a process called deamination which involves removal of amino group from amino acid to form ammonia.Ammonia is a toxic product especially for mammals which do not have enough water in their bodies ( unlike organisms like bony fish). Therefore mammals turn the toxic ammonia into less toxic product called urea through a series of reactions in the ornithine cycle as discussed aboveOrnithine, arspatate, arginine are all amino acids.


The ornithine cycle, also known as the urea cycle, is a metabolic pathway that takes place in the liver and other tissues. It is responsible for the synthesis of urea and the detoxification of ammonia, which is a byproduct of protein metabolism. The liver plays a crucial role in this cycle by converting ammonia into urea, which can then be excreted by the kidneys.

Deamination is another important process in protein metabolism, which involves the removal of the amine group from an amino acid. This process also generates ammonia, which can be toxic to the body if it accumulates. Once again, the liver plays a critical role in removing ammonia from the body by converting it into urea, which can be safely excreted in urine.

Overall, the liver is essential for maintaining the body's nitrogen balance and preventing accumulation of toxic ammonia. Dysfunction of the liver, such as in liver disease or damage, can result in impaired ornithine cycle and deamination, leading to harmful levels of ammonia buildup in the body.