All biological tissues contain amino acids. All amino acids except glycine (the simplest one) are optically active, having a stereocenter at their α-C atom. This means that the amino acid can have two different configurations, "D" or "L" which are mirror images of each other.
Amino acids are present in biological tissues. Except for glycine (the simplest one), all amino acids show optical activity with a stereocenter at their α-C atom. This indicates that the amino acid can have two different orientations, "D" or "L," which are mirror images of each other.