3D Amino Acids - Amino acids are organic compounds that contain amino[a] (−NH+3) and carboxylic acid (−CO2H) functional groups, along with a side chain (R group) specific to each amino acid. The elements present in every amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) (CHON). In addition sulfur (S) is present in the side chains of cysteine and methionine, and selenium (Se). Click here