Molecular model of Arginine (C6. H14. N4. O2), a conditionally essential, genetically coded, amino acid (is only essential in juveniles). It is a complex amino acid, often found at active site in proteins and enzymes due to its amine-containing side chain. Arginine plays an important role in nitrogen metabolism and acts as intermediate in the urea cycle and in detoxification of nitrogenous wastes. Atoms are represented as spheres and are colour-coded: carbon (black), hydrogen (white), Nitrogen (blue), and Oxygen (red). Illustration.