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Amino acids function: building blocks of proteins

Proteins are of primary importance to the continuing functioning of life on Earth. Proteins catalyze the vast majority of chemical reactions that occur in the cell. They provide many of the structural elements of a cell, and they help to bind cells together into tissues. Some proteins act as contractile elements to make movement possible. Others are responsible for the transport of vital materials from the outside of the cell (“extracellular”) to its inside (“intracellular”). Proteins, in the form of antibodies, protect animals from disease and, in the form of interferon, mount an intracellular attack against viruses that have eluded destruction by the antibodies and other immune system defenses. Many hormones are proteins. Last but certainly not least, proteins control the activity of genes (“gene expression”).

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.

What are vitamins, and how do they work?

Vitamins are organic compounds that people need in small quantities. Most vitamins need to come from food because the body either does not produce them or produces very little. Each organism has different vitamin requirements. For example, humans need to get vitamin C from their diets — while dogs can produce all the vitamin C that they need.

Fat-soluble vitamins

Vitamins A, D, E, and K are fat-soluble. The body storesTrusted Source fat-soluble vitamins in fatty tissue and the liver, and reserves of these vitamins can stay in the body for days and sometimes months. Dietary fats help the body absorb fat-soluble vitamins through the intestinal tract.