Why are amino acids chiral?

1 Answer

All amino acids except glycine are chiral because they all contain at least one chiral centre.

The general formula for an amino acid is

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The central carbon has four different groups attached. So the compound can exist as a pair of nonsuperimposable mirror images.

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Thus, we can have D- and L-isomers of amino acids.

A rule of thumb for determining the D/L isomeric form of an amino acid is the "CORN" rule.

You arrange the groups CO OH, R, N, and H so that the H atom is pointing away from you.

If the arrangement of the CORN groups is counterclockwise, it is the L form.

All amino acids found in proteins have the L-configuration.

D-amino acids are not naturally found in proteins. They are not involved in the metabolic pathways of eukaryotic organisms.

D-amino acids are important in the structure and metabolism of bacteria. For example, D-alanine (below) is a structural component of certain bacterial cell walls.

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