A peptide is a short chain of amino acids. The amino acids in a peptide are connected to one another in a sequence by bonds called peptide bonds. Typically, peptides are distinguished from proteins by their shorter length, although the cut-off number of amino acids for defining a peptide and protein can be arbitrary.Peptides are short chains of between two and fifty amino acids, linked by peptide bonds. Chains of less than ten or fifteen amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptide