Amino acid which is optically ine ?

The a-carbon of amino acids has four different groups attached to it and so is a chiral or asymmetric carbon. Hence, there are two possible enantiomers, L and D, i.e., mirror image with refrence to a-carbon. The chiral carbon is also responsible for optical activity and stereoisomerism. Only exception is glycine, which is the simplest amino acid. Glycine has no chiral carbon (chirality) because a-carbon of glycine does not have four different groups attached to it. Therefore glycine does not have optical activity or D and L forms (enantiomers).