# What are the optical isomers of amino acids?

Alpha- amino acids have a central carbon atom with a tetrahedral arrangements of bonds around it, to which $- H$, $- C O O H$, $- N {H}_{2}$ and an $- R$ group are bonded. So long as the $- R$ group is different to the other three then there are two distinctly different stereoisomers that can be formed. These are best represented by their mirror images, drawing the 3D structures as shown here for alanine: