Essential amino acids are those which cannot be synthesised by organisms in the body and are obtained from plants, e.g., valine, leucine, isoleucine, phenylalanine, threonine, lysine, tryptophan, methionine. Non-essential amino acids can be synthesised by the organism and may not be the requisite components of diet, e.g., serine, cysteine, proline, glycine, alanine, asparagine, glutamine and tyrosine.