Peptides
A peptide is a short chain of amino acid monomers linked by peptide bonds. It is a type of organic compound that is made up of two or more amino acids, and can be either naturally occurring or synthetic. Peptides can have a variety of functions, including acting as hormones, neurotransmitters, and enzymes. Peptides are involved in many processes within the body, such as protein synthesis, cell signaling, and gene regulation.
Peptides (from Ancient Greek πεπτός (peptós) 'digested', from πέσσειν (péssein) 'to digest') are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
blue marked carboxyl end (L-alanine)
A polypeptide is a longer, continuous, unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological polymers and oligomers, alongside nucleic acids, oligosaccharides, polysaccharides, and others.
A polypeptide that contains more than approximately 50 amino acids is known as a protein. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, or to another protein or other macromolecule such as DNA or RNA, or to complex macromolecular assemblies.
Amino acids that have been incorporated into peptides are termed residues. A water molecule is released during formation of each amide bond. All peptides except cyclic peptides have an N-terminal (amine group) and C-terminal (carboxyl group) residue at the end of the peptide (as shown for the tetrapeptide in the image).
