The three parts of an amino acid are the amino group, the carboxyl group, and the?

The Answer is "R" group.

Amino acids are organic compounds and have two carbon bonds. The three parts of an amino acid are the amino group, the carboxyl group, and the R group. In amino acids, alpha carbon is bonded to hydrogen atom and the other groups. That R group is different in amino acids and shows how the protein monomers are different from each other.

The last group that is included is the R Group.