2.2.4.E. Classification Based on Chemical Constitution

1. Small amino acids:– Glycine, Alanine
2. Branched amino acids:– Valine, Leucine, Isoleucine
3. Hydroxy amino acids (-OH group):– Serine, Threonine
4. Sulfur amino acids:– Cysteine, Methionine
5. Aromatic amino acids:– Phenylalanine, Tyrosine, Tryptophan
6. Acidic amino acids and their derivatives:– Aspartate, Asparagine, Glutamate, Glutamine
7. Basic amino acids:– Lysine, Arginine, Histidine
8. Imino acid:- Proline
9. Special/Newly Added amino acids:- Pyrrolysine, Selenocysteine

2.2.5. Essential Amino Acids in Humans

2.2.6. Non-Essential Amino Acids in Humans