Peptides (from Ancient Greek πεπτός (peptós) 'digested', from πέσσειν (péssein) 'to digest' are short chains of amino acids linked by peptide bonds. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides , and tetrapeptides. 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.
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