Nitrogenous Wastes Concentrations of waste produ ust be ke proteins to a minimum in the ody. Amino groups from protein tabolism forr ammonia, a highly toxIc substance. The ammonia can be converted to urea or uric acid. which are ammonia urea unic acid less toxic, but this is energetically H expensive. Different H N·H groups of organisms H2N-C-NH2O-G-NN have different nitrogenous waste roducts eded to excrete energy needed to produce