What is the general structure of an amino acid?

The general structure of an amino acid is simple and the same for all amino acids, except for one part that changes (the side chain).

Here’s how it looks and works:

Each amino acid has four main parts attached to a central carbon atom (called the alpha carbon, Cα):

1. Amino group (–NH₂) → a basic group.
2. Carboxyl group (–COOH) → an acidic group.
3. Hydrogen atom (–H).
4. Side chain (–R group) → this part is different for each amino acid and gives it unique properties.

General formula:
NH₂–CH(R)–COOH

Example:

• For glycine, R = H
• For alanine, R = CH₃

In short:
An amino acid has a central carbon with an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group) attached to it.
This structure makes amino acids the building blocks of proteins.