An Organic compound with an amino group bound to a Carbon atom (known as $\alpha$), which is itself bound to a Hydrogen, and a Carboxyl group (making it an acid). The $\alpha$ carbon is also bound to a side chain.

Categories of biological amino acids

Charge refers to the charge at neutral pH. They have a 3 letter code to identify them

Polar; uncharged

Polar; negatively charged

Polar; positively charged

Non-polar

Hydrophobic

Special

Proline, which is technically an Imino acid, instead of an amino aicid. Cysteine, which can make a covalent disulfide bond.

All amino acids in Humans are L (see Chiral molecule), but Bacteria have both