Dictionary of Biological Psychology
Chains of two or more AMINO ACIDS. Adjacent amino acids are linked together by a chemical bond called a peptide bond (a single bond between a nitrogen and carbon molecule). Peptides are different from PROTEINS only in that they are smaller; a peptide is considered to be less than 10 kilodaltons in molecular weight.
In terms of structure, one end of the peptide has an amino group at one end (referred to as the N-terminus) and a carboxyl group at the other. Since all peptides have these structural features in common, the individual chemical identity of different peptides is rendered by the existence of differing side-chains. Like proteins, peptides are synthesized in the RIBOSOMES of cells, where MESSENGER RNA codes for their structure. Peptides are broken down by a type of ENZYME called PEPTIDASE. Peptides in the nervous system, called NEUROPEPTIDES, act as NEUROTRANSMITTERS and neuromodulators (see NEUROMODULATION) and have an important role in neural signalling.
ANN E.KELLEY
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