All the amino acids but glycine are chiral molecules. That is, they exist in two optically active, asymmetric forms (called enantiomers) that are the mirror images of each other. (This property is conceptually similar to the spatial relationship of the left hand to the right hand.) One enantiomer is designated D and the other L. It is important to note that the amino acids found in proteins almost always possess only the L-configuration. This reflects the fact that the enzymes responsible for protein synthesis have evolved to utilize only the L-enantiomers. Reflecting this near universality, the prefix L is usually omitted. Some D-amino acids are found in microorganisms, particularly in the cell walls of bacteria and in several of the antibiotics. However, these are not synthesized in the ribosome.
The-linking-of-atoms-in-a-peptide-bondThe linking of atoms in a peptide bond.[Credits : Encyclopædia Britannica, Inc.]
Portion-of-polynucleotide-chain-of-deoxyribonucleic-acid-The-inset-showsPortion of polynucleotide chain of deoxyribonucleic acid (DNA). The inset shows the corresponding …[Credits : Encyclopædia Britannica, Inc.]
Red-blood-cells-trapped-in-a-mesh-of-fibrin-threadsRed blood cells (erythrocytes) trapped in a mesh of fibrin threads. The glycoprotein prothrombin, …[Credits : Eye of Science / Photo Researchers, Inc.]
Family-relationships-in-amino-acid-biosynthesesFigure 10: Family relationships in amino-acid biosyntheses. Components of proteins are underlined. …
General-scheme-of-protein-and-amino-acid-metabolismGeneral scheme of protein and amino acid metabolism.[Credits : Encyclopædia Britannica, Inc.]
Link to this article and share the full text with the readers of your Web site or blog-post.
If you think a reference to this article on "amino acid" will enhance your Web site,
blog-post, or any other web-content, then feel free to link to this article,
and your readers will gain full access to the full article, even if they do not subscribe to our service.
You may want to use the HTML code fragment provided below.
We welcome your comments. Any revisions or updates suggested for this article will be reviewed by our editorial staff. Contact us here.
Regular users of Britannica may notice that this comments feature is less robust than in the past. This is only temporary, while we make the transition to a dramatically new and richer site. The functionality of the system will be restored soon.