Glutamine is classified as an α-amino acid. It's a charge-neutral, polar amino acid.
Glutamine (Gln or Q) plays a vital role in protein biosynthesis. Its structure closely resembles that of glutamic acid, the key difference being the replacement of the carboxylic acid group with an amide group in its side chain. This structural feature contributes to its classification as a polar amino acid due to the presence of the amide group, which can form hydrogen bonds. Because it is an α-amino acid, it shares the same basic structure with all amino acids: a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a distinctive R-group (in glutamine's case, a specific amide-containing side chain). It's considered "charge-neutral" because, at physiological pH, its side chain carries no net electrical charge.
