Amino acids are essential or non essential. Essential amino acids are those that are not present in the body and thus are obtained from the diet. Non essential amino acids are those that are present in the body. Essential amino acids are Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Alanine, Leucine, Lysine. Apart from this all other amino acids are non essential amino acids.