The final end product of certain native or dietary proteins, especially the nucleoproteins found in the nucleus of cells. Unlike the much smaller nitrogenous waste product urea, which is mostly recycled to form many amino acids, uric acid is an unrecyclable metabolite. It is a bent nail that won't restraighten, and it must be excreted: nucleoprotein to purine to uric acid to the outside in the urine or the sweat. (See GOUT, PURINES.)