noun, plural: polypeptides
A polymer of amino acids joined together by peptide bonds
A polymer produced by a living organism is called a biopolymer. There are three major classes of biopolymers: (1) polysaccharides, (2) polypeptides, and (3) polynucleotides. A polypeptide is an unbranched peptide, often comprised of about a hundred amino acids. It can be in the form of a long, continuous, unbranched chain of peptides linked together by peptide bonds. Thus, it is also referred to as a polypeptide chain. A peptide is a short chain comprised of amino acid monomeric subunits. The peptide bond occurs between the carboxyl group of one amino acid and the amine group of the next amino acid. The peptides may be named based on the number of monomeric amino acids that comprise it. For instance, a tripeptide is a peptide comprised of three amino acid sub-units.
One or more polypeptides that occur together and function in a particular way are referred to as proteins. Proteins are often bound to ligands (e.g. coenzymes), to another protein, or to other macromolecules (DNA, RNA, etc.)
Word origin: Greek polýs (many) + peptide