Which amino acid is known to be non-chiral?

The amino acid known to be non-chiral is glycine. Chiral molecules are those that have non-superimposable mirror images, which usually occurs in amino acids that have a central carbon atom (the alpha carbon) attached to four different substituents. In the case of glycine, its structure is unique because it has two hydrogen atoms attached to the alpha carbon. This means that there are not four distinct substituents bonded to the alpha carbon, and hence glycine cannot exist in two mirror image forms, which is a requirement for chirality. As a result, glycine is termed non-chiral, while other amino acids like alanine, valine, and serine have chiral centers and can exist as different enantiomers.