Which of the following amino acids is known to exhibit optical activity?

The correct answer is glutamate, as it is one of the amino acids that exhibits optical activity. Optical activity arises from the presence of a chiral center in a molecule—specifically, a carbon atom bonded to four different groups, which results in two enantiomers that can rotate plane-polarized light in different directions.

Glutamate, like most amino acids (except glycine), contains a central carbon atom (alpha carbon) that is bonded to an amino group, a carboxyl group, a hydrogen atom, and a distinctive side-chain (the variable group). This structure provides the asymmetry necessary for optical activity, allowing glutamate to exist in two enantiomeric forms.

Glycine, in contrast, does not exhibit optical activity because its side chain is a hydrogen atom, which means it does not have four different substituents attached to the alpha carbon, rendering it achiral. Valine and alanine do possess chiral centers and are also optically active; however, glutamate's presence as an amino acid that specifically functions in metabolism and neurotransmission makes it a significant representative of optical activity in a biological context. Thus, while B is chosen, note that other options may also contribute to optical activity despite the