The other group is the amino group. The third group is the H atom. And the final group is the side chain, the R group, that is unique to that particular amino acid. So 19 out of the 20 amino acids are Chiral, because this R group is not the same as these other three groups. But for Glycine, as we'll see in Lex lecture, this R group is actually an H atom. So glycine is not chiral.