Amino acids are divided into two categories based on protein structure.
1. Protein amino acid: All the amino acids that form proteins are called protein amino acids. Protein is 20 amino acids. Glycine, lysine, valine, alanine, tyrosine, leucine, isoleucine, aspartic acid, glutamic acid, asparagine, glutamine, arginine, cystine, serine, methionine, threonine, phenylalanine, histidine, tryptophan and proline.
2. Non-protein amino acid: All the amino acids that do not participate in the formation of proteins are called non-protein amino acids. More than 700 non-protein amino acids. Of these, 300 are found in plants. Such as Ornithine, Homoserine, Homocysteine, Citrulline etc.