Urea Biosynthesis

High concentrations of ammonia are dangerous, especially for brain tissue (causing unconsciousness, coma and agitation). Ammonia can pass through membranes and enter brain cells, as well as mitochondria. The ornithine cycle takes place in the liver (cytosol and mitochondria). The formed urea is transported to the kidneys and excreted from the body through urine. The general formula is 2 NH3 + CO2 + 3ATP > urea + H2O + 3 ADP • About 85% of ammonia is neutralized in the liver in the ornithine cycle.