Peptides (from Gr. ÏÎµÏÏÏÏ, "digested", derived from ÏÎÏÏÎµÎ¹Î½, "to digest") are short chains of amino acid monomers linked by peptide (amide) bonds, the covalent chemical bonds formed when the carboxyl group of one amino acid reacts with the amino group of another. Peptides are distinguished from proteins on the basis of size, and as a benchmark can be understood to contain approximately 50 amino acids or less. The shortest peptides are dipeptides, consisting of 2 amino acids joined by a single peptide bond, followed by tripeptides, tetrapeptides, etc. A polypeptide is a long, continuous, and unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological oligomers and polymers, alongside nucleic acids, oligo- and polysaccharides, etc.
It seems you can blame everything on drugs, as researchers show that the human brain manufactures proteins that act on specific receptors in the same way that marijuana does; those receptors are actually situated in the brain itself. This discovery was published online in the FASEB journal, and Gerald Weissmann, M.D., Editor-in-Chief of the journal [...]