What are two functional groups found in every amino acid?

An amino acid is a molecule that contains two functional groups, an amine and a carboxylic acid, as shown in Figure 1. In this illustration there is an additional group called the side chain, designated with an R. The variation seen in naturally occurring amino acids arises from differences in this side chain.

peptide bonds join the carboxyl of amino acids. When activated, carboxyllic acids and amines form amides. Amino acids are bifunctional, with each amino acid having both amino and carboxyl groups.