Which of the following amino acids contains an amide group?

Glutamine is the amino acid that contains an amide group. It features a side chain that includes an amide functional group (–C(NH2)=O), which is characteristic of both glutamine and asparagine. This amide group is formed from the carboxylic acid functional group of the side chain through the addition of an amine group.

In the case of glutamine, this functional group plays essential roles in metabolism and protein synthesis, as the amide group can participate in various biochemical reactions. For example, it can act as a nitrogen donor in the synthesis of nucleotides and other biomolecules.

The other amino acids listed do not have an amide group; glycine is the simplest amino acid with a hydrogen as its side chain, leucine is a branched-chain amino acid with a hydrophobic side chain, and phenylalanine contains a benzyl side chain. None of these structures include the distinctive amide functional group that is present in glutamine.