Amino acid structural formula general formula is shown in the figure. It is made up of the functional groups of amino (-NH2) and carboxylic (-COOH) groups, as well as the side chains attached to each amino acid.

The specific chemical formula is RCH(NH2)COOH, and amino acids can be classified as α, β, γ, δ...... and so on, depending on where the amino group is linked to the carbon atom in the carboxylic acid: α-amino acids have the amino group and the carboxyl group linked to the same carbon atom, β-amino acids have the amino group and the carboxyl group linked to the neighboring carbon atoms, β amino acids have amino and carboxyl groups attached to neighboring carbon atoms, and so on.

Physical and chemical properties of amino acids:

All are colorless crystals. Melting point is about 230 ℃ above, most of them do not have the exact melting point, melting decomposition and release CO2; can be soluble in strong acids and strong alkali solutions, except cystine, tyrosine, diiodothyronine, are soluble in water; except for proline and hydroxyproline, are difficult to dissolve in ethanol and ether.

Has amphoteric properties. There are three types of alkaline [diaminocarboxylic acid, such as lysine (lysine)]; acidic [monoamino diaminocarboxylic acid, such as glutamic acid (Glutamic acid)]; neutral [monoamino monocarboxylic acid, such as alanine (Alanine)]. Most amino acids are acidic or basic to varying degrees, but fewer are neutral. Therefore, they can combine with both acids and bases to form salts.

Reference: Baidu Encyclopedia-Amino Acids