Amino Acid Structure

We divide amino acids into four general categories (with two special cases).

1. Hydrophobic, which have nonpolar side chains that are usually aliphatic. Aliphatic means the side chains they have only have carbon and hydrogen atoms in their R groups (and no resonance).
2. Aromatic, which have one or more aromatic rings in the side chains.
3. Polar, which have polar, uncharged side chains.
4. Charged, which have either positively or negatively charged side chains
5. And the special cases: glycine (its R group is a hydrogen atom), and proline

20 amino acids coded for in our genome.
General structure = Central alpha carbon bound to: Hydrogen atom, Carboxylic acid group, Amino group, Variable R Group (differentiates the AA).