Amino acids are the monomers that form peptides and proteins. There are 20 different amino acids that contain an amino group (NH2), carboxyl group (COOH) and R-group. The general formula is: RCH(NH2)COOH.
These 3 groups are all bonded to the same carbon called the alpha-carbon. This carbon is also bonded to a hydrogen. The properties of an amino acid depend on its R-group.