- any of a class of organic compounds that contains at least one amino group, –NH2, and one carboxyl group, –COOH: the alpha-amino acids, RCH(NH2)COOH, are the building blocks from which proteins are constructed.
- any of a group of organic compounds containing one or more amino groups, -NH 2, and one or more carboxyl groups, -COOH. The alpha-amino acids RCH(NH 2)COOH (where R is either hydrogen or an organic group) are the component molecules of proteins; some can be synthesized in the body (nonessential amino acids) and others cannot and are thus essential components of the diet (essential amino acids)
- Any of various organic acids containing both an amino group and a carboxyl group, especially any of the 20 or more compounds that link together to form proteins.
- Any of a large number of compounds found in living cells that contain carbon, oxygen, hydrogen, and nitrogen, and join together to form proteins. Amino acids contain a basic amino group (NH2) and an acidic carboxyl group (COOH), both attached to the same carbon atom. Since the carboxyl group has a proton available for binding with the electrons of another atom, and the amino group has electrons available for binding with a proton from another atom, the amino acid behaves as an acid and a base simultaneously. Twenty of the naturally occurring amino acids are the building blocks of proteins, which they form by being connected to each other in chains. Eight of those twenty, called essential amino acids, cannot be synthesized in the cells of humans and must be consumed as part of the diet. The remaining twelve are nonessential amino acids.
Basic organic molecules (see also organic molecule) that combine to form proteins. Amino acids are made up of hydrogen, carbon, oxygen, and nitrogen. Some examples of amino acids are lysine, phenylalanine, and tryptophan.