Several amino acids are intermediates of the urea cycle, having side ammonia groups that join with free carbon dioxide (CO2) and ammonia to produce net excretion of ammonia as urea. Which of the following amino acids has a nitrogen in its side chain and is an intermediate of the urea cycle? A. ArginineB. PhenylalanineC. MethionineD. GlutamateE. Asparagine

A. Arginine

Explanation:

The urea cycle is the cycle of the biochemical reactions which produces urea from ammonia.

Steps of the urea cycle:

Carbamoyl phosphate, in presence of ornithine transcarbamoylase is converted to citrulline by the denotation of carbamoyl phosphate groupto ornithine and a phosphate group is released. Amino group of the aspartate and carbonyl group of the citrulline are condensed to form argininosuccinate in the presence of enzyme, argininosuccinate synthetase. This condensation reaction is ATP dependent. Argininosuccinate then undergoes cleavage by the argininosuccinase to form intermediate, arginine and fumarate. Arginine is then cleaved by the arginase to form urea as well as ornithine. Ornithine is transported back to mitochondria to begin urea cycle again.