A group of chemical compounds that form the basic structural units of all proteins. Each amino acid molecule consists of amino and carboxyl groups of atoms linked to a variable chain or ring of carbon atoms. Individual amino acid molecules are linked together by chemical bonds called peptide bonds to form short chains of molecules called polypeptides. Hundreds of polypeptides are, in turn, linked together, also by peptide bonds, to form a protein molecule. What differentiates one protein from another is the sequence of the amino acids. There are 20 different amino acids that make up all the proteins in the body. Of these, 12 can be made by the body; they are known as nonessential amino acids because they do not need to be obtained from the diet. The other 8, known as the essential amino acids, cannot be made by the body and must therefore be obtained from the diet.
Amino acids |
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