Nitrogen, Nitrogen Cycle and Excretion of Nitrogen

The daily protein turnover of a human being is approximately 300 g. Amino acids contain nitrogen atoms, which need to be eliminated by the body without developing too much toxic ammonia. Here, urea comes into play as an appropriate end product of protein degradation. The steps of synthesis in the urea cycle (also: ornithine cycle), which occurs in the liver, should be well understood. By the way, the urea cycle was first described in 1932 and is therefore the first described cyclic metabolic pathway.