It is hardly surprising that much of the early biochemical research was concerned with the study of proteins.Proteins form the class of biological macromolecules that have the most well-defined physico- chemical properties and consequently are generally easier to isolate and characterize than nucleic acids,polysaccharides,or lipids. Furthermore,proteins,particularly in the forms of enzymes,have an obvious biochemical function.The central role that proteins play in biological processes has therefore been recognized since the earliest days of biochemistry.In contrast,the task of nucleic acids in the transmission and expression of genetic information was not realized until the late 1940s,the role of lipids in biological membranes was not appreciated until the 1960s,and the biological functions of polysaccharides are still somewhat mysterious. (Donald Judith Voet,1990) Carbohydrate metabolism