The simplest member of this group is glycine, where the saturated carbon atom is unsubstituted, rendering it optically inactive. Molecular Expressions has been nominated as a candidate for the 2001 Webby Awards in the sciences category. If you enjoy this site, please assist us by casting your vote in the People's Voice Awards balloting. The rest of the 20 most common amino acids are optically active existing as both D and L stereoisomers. There are also acidic and basic side chains as well as thiol chains that can be oxidized to dithiol linkages between two similar amino acids.
Amino acids are the principal building blocks of proteins and enzymes.
They are incorporated into proteins by transfer RNA according to the genetic code while messenger RNA is being decoded by ribosomes. During and after the final assembly of a protein, the amino acid content dictates the spatial and biochemical properties of the protein or enzyme. The amino acid backbone determines the primary sequence of a protein, but the nature of the side chains determines the protein's properties. Amino acid side chains can be polar, non-polar, or practically neutral. Polar side chains tend to be present on the surface of a protein where they can interact with the aqueous environment found in cells.