CAS CH 203 Lecture Notes - Lecture 4: Mit Opencourseware, Cellular Respiration, Electron Transport Chain
Document Summary
Quaternary structure using hb as an example and mb for comparison. Many proteins are composed of more than one polypeptide chain. You have already seen this with the collagen. Quaternary structure can provide a basis for regulation at a distance: allosteric regulation and cooperative behavior. We will see when studying metabolic pathways, that many of the enzymes that control the flux through the pathway (rate-limiting step(s)) have quaternary structures and exhibit cooperative behavior by binding small molecule metabolites. However, there are many other proteins composed of multiple polypeptide chains where the chains act independently: big picture: mb and hb have different physiological roles. Mb is a monomer and is found in tissues. It functions as a carrier of o2 to the mitochondrial in a cell. O2 has limited solubility (0. 1 mm) and thus a carrier is required for rates of distribution to be sufficient for metabolism.
