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In biochemistry, this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent.

In the alpha amino acids, the amino and carboxylate groups are attached to the same carbon, which is called the α-carbon.

The various alpha amino acids differ in which side chain (R group) is attached to their alpha carbon.

They can vary in size from just a hydrogen atom in glycine, through a methyl group in alanine, to a large heterocyclic group in tryptophan. Beyond the amino acids that are found in all forms of life, many non-natural amino acids are also important.

The chelating agents EDTA and nitriloacetic acid are alpha amino acids that are industrially synthesized (sometimes from naturally occurring amino acids). Alpha-amino acids are the building blocks of proteins.

A protein forms via the condensation of amino acids to form a chain of amino acid "residues" linked by peptide bonds.

Proteins are defined by their unique sequence of amino acid residues; this sequence is the primary structure of the protein.

Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a huge variety of proteins. Twenty standard amino acids are used by cells in protein biosynthesis, and these are specified by the general genetic code.

These twenty amino acids are biosynthesized from other molecules, but organisms differ in which ones they can synthesize and which ones must be provided in their diet.

The ones that cannot be synthesized by an organism are called essential amino acids.