The biochemistry of sugars.

In animal cells the utilization of sugars involves one or more of the three major pathways known to occur in these cells. The glycolytic (Embden-Meyerhof) pathway is quantitatively the most important, and this pathway, coupled to the citric acid cycle, serves as a major source of energy. Glycolysis and the citric acid cycle also provide most of the precursors for the synthesis of proteins, nucleic acids and lipids. The pentose phosphate, or hexose monophosphate oxidation, pathway is a major source of NADPH required for the conversion of carbohydrate to the more reduced lipids and proteins, and also furnishes the ribose and deoxyribose moieties of nucleotides and nucleic acids. The functions of the third pathway, the uronic acid pathway, are less well defined. It is the source of glucuronides for mucopolysaccharides and for detoxification mechanisms, and also in most animals, is the pathway for the synthesis of ascorbic acid. The uronic acid pathway may also function as a point of entry for glucuronides, pentoses, and pentitols.