specific shorter lengths are named using IUPAC numerical multiplier prefixes: A monopeptide has one amino acid. A dipeptide has two amino acids. A tripeptide has three amino acids. A tetrapeptide has four amino acids. A pentapeptide has five amino acids. (e.g., enkephalin). A hexapeptide has six amino acids. (e.g., angiotensin IV). A heptapeptide has seven amino acids. (e.g., spinorphin). An octapeptide has eight amino acids (e.g., angiotensin II). A nonapeptide has nine amino acids (e.g., oxytocin). A decapeptide has ten amino acids (e.g., gonadotropin-releasing hormone and angiotensin I). A undecapeptide has eleven amino acids (e.g., substance P). The same words are also used to describe a group of residues in a larger polypeptide (e.g., RGD motif). Function A neuropeptide is a peptide that is active in association with neural tissue. A lipopeptide is a peptide that has a lipid connected to it, and pepducins are lipopeptides that interact with GPCRs. A peptide hormone is a peptide that acts as a hormone. A proteose is a mixture of peptides produced by the hydrolysis of proteins. The term is somewhat archaic. A peptidergic agent (or drug) is a chemical which functions to directly modulate the peptide systems in the body or brain. An example is opioidergics, which are neuropeptidergics. A cell-penetrating peptide is a peptide able to penetrate the cell membrane. See also Acetyl hexapeptide-3 Beefy meaty peptide Collagen hybridizing peptide, a short peptide that can bind to denatured collagen in tissues Bis-peptide CLE peptide Epidermal growth factor Journal of Peptide Science'' Lactotripeptides Micropeptide Multifunctional peptide Neuropeptide Palmitoyl pentapeptide-4 Pancreatic hormone peptide spectral library Peptide synthesis Peptidomimetics (such as peptoids and β-peptides) to peptides, but with different properties. Protein tag, describing addition of peptide sequences to enable protein isolation or detection Replikins Ribosome Translation (biology) References Peptides