This document classifies amino acids into three categories: neutral, basic, and acidic. Neutral amino acids are further divided into aliphatic amino acids with hydrocarbon or specific functional groups, aromatic amino acids with phenyl/phenol rings, and heterocyclic amino acids with indole or pyrrolidine rings. Basic amino acids contain an additional amine group and include the aliphatic lysine and arginine and the cyclic histidine. Acidic amino acids are dicarboxylic and comprised of aspartic acid and glutamic acid.

1. By: Olla S. BaEissa
Chemical Classification
(A) Neutral amino acids (monoamine, monocarboxylic amino acids)
1) Neutral Aliphatic amino acids
I- with hydrocarbon side chain
Glycine , Alanine , Valine , Leucine , isoleucine
II- with specific groups
i- Sulfer group
Cysteine , Homocysteine , Methionine
ii- hydroxyl group
Serine , Homoserine , Threonine , Hydroxylysine
iii- carboxy amide group
Asparagine , Glutamine
2) Neutral Aromatic amino acids (phenyl/phenol ring)
Phenylalanine , Tyrosine
3) Neutral Heterocyclic amino acids
- Indole ring: Tryptophan
- Pyrrolidine ring: Proline & Hydroxyproline (Imino group)
(B) Basic amino acids (diamine, monocarboxylic amino acids)
> Aliphatic: Lysine , Arginine
> cyclic (imidazole): Histidine
(C) Acidic amino acids (monoamine, dicarboxylic amino acids)
- Aspartic acid: Aspartate
- Glutamic acid: Glutamate