The three parts are amino group, carboxyl group, and R group,
Amino acids are the basis of the constitution of proteins and other peptides, even if they are not the only constituents (see, for example, heme, prosthetic group of hemoglobin). This article aims to review the main characteristics common to all amino acids, as well as the particular properties of the main amino acids found in living molecules.
The molecule has two ionizable groups: one acid (COOH <-> COO - + H +), the other basic (NH 2 + H + <-> NH3 +). The carbon atom to which the amine-NH 2 group is attached and the carboxylic acid-COOH group is called alpha carbon convention.
The group R corresponds to a variable radical depending on the amino acid in question. It is therefore he who determines the nature of the amino acid since the rest is invariant.