Ammonia Transport and Detoxification
Start with the big picture
Ammonia arises from several metabolic sources, including amino acid deamination, gut bacterial activity, and the breakdown of purines, pyrimidines, and amines. Because free ammonia is toxic, blood carries nitrogen mainly in the water-soluble forms glutamine and alanine. Glutamine synthetase captures ammonia, while glutaminase releases it in tissues such as the liver, kidney, and gut; the kidney can excrete ammonia as ammonium to help buffer acid. The glucose–alanine cycle transfers nitrogen from muscle to liver. In the liver, the urea cycle converts ammonia to urea, with its activity shaped by enzyme regulation and cellular compartmentation. Disruption of these processes can cause hyperammonemia, including in acquired liver disease and inherited urea cycle defects.
What you'll learn
- Identify major metabolic sources of ammonia.
- Explain how glutamine and alanine transport nitrogen in blood.
- Describe the roles of glutamine synthetase and glutaminase.
- Outline nitrogen transfer in the glucose–alanine cycle and urea cycle.
- Recognize key biochemical patterns associated with OTC and CPS1 deficiency.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
