Figure 2: Reactions of urea cycle (NAG—N-acetylglutamate; in the formation of urea , one amino group is derived from free ammonium ion while the other is from aspartate; carbon is obtained from CO2; " mitochondrial enzymes, the rest of the enzymes are cytosomal). What is the urea cycle . Where does it occur. What is the function of the pathway. Learn the pathway with steps, regulations, and a diagram. Urea is formed, enters the bloodstream, is filtered by the kidneys, and is eventually excreted in the urine. The biochemical part of excretion is urea synthesis using the urea cycle , also known as the Ornithine Cycle. It is also known as the Kreb-Henseleit cycle and occurs in the liver. The conversion of ammonia into urea through a series of biochemical reactions is known as the urea cycle or ornithine cycle. It takes place in the liver with the help of mitochondrial and cytosolic enzymes.
