Lysine. Molecular model of the amino acid lysine. Its chemical formula is C6.H14.N2.O2. Atoms are represented as balls and are colour- coded: carbon (blue), hydrogen (gold), oxygen (red) and nitrogen (dark blue). Amino acids are the building blocks of proteins. Lysine is an essential amino acid. It cannot be synthesised by the body and so needs to be obtained from food. It is most concentrated in watercress, soya bean, carob bean, green beans, lentils and spinach. Lysine plays a large role in calcium absorption, building muscle tissue, injury recovery and in the production of hormones, enzymes and antibodies.