noun
: an organic acid in which a portion of the nonacid hydrogen has been replaced by one or more amino groups and which therefore shows both basic and acidic properties ; especially : one of the more than 20 alpha-amino acids, most of which have the general formula RCH(NH 2 )COOH, that are synthesized in plant and animal tissues, that are considered the building blocks of proteins, from which they can be obtained by hydrolysis, and that play an important role in metabolism, growth, maintenance, and repair of tissue — see essential amino acid , peptide