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This chapter describes two ancient metabolic pathways common to all cells in the body, glycolysis and the pentose phosphate pathway. The RBC, which lacks mitochondria and the capability for oxidative metabolism and obtains all of its ATP energy by glycolysis, is used as a model for introducing these pathways. Anaerobic glycolysis in the RBC provides a limited amount of ATP by conversion of the six-carbon sugar, glucose , to two molecules of the three-carbon hydroxyacid, lactate. Through a series of sugar phosphate intermediates, glycolysis provides metabolites for branch points to
numerous other metabolic pathways, including the pentose phosphate pathway. This pathway provides pentoses for synthesis of DNA and RNA in nucleated cells, and NADPH for biosynthetic reactions. NADPH is also required for maintenance of reduced glutathione, which is an essential cofactor for antioxidant defense systems that protect the cell against oxidative stress.
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- Why was glucose selected as blood sugar during evolution, rather than other sugars, e.g. galactose, fructose or sucrose?
- Describe coupled enzymatic reactions, using only red cell enzymes, that could be used to measure blood glucose and lactate concentrations.
- Which test procedure is used for measuring blood glucose in your local hospital? Discuss the principles and normal values for this assay.
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Arya R, Layton DM, Bellingham AJ. Hereditary red cell enzymopathies. Blood Reviews 1995;9:165-175.
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| Brown SP, Keith WB. The effect of acute exercise on levels of erythrocyte 2,3-bisphosphoglycerate: a brief review. J Sports Med 1993;11:479-484.
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| Knull H, Minton AP. Structure within eukaryotic cytoplasm and its relationship to glycolytic metabolism. Cell Biochemistry and Function 1996;14:237-248.
Full article
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| Mehta A, Mason PJ, Vulliamy TJ. Glucose-6-phosphate deficiency. Baillière's Clinical Hematology 2000;13:21-38.
Full article
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| McMullin M. The molecular basis of disorders of red cell enzymes. J Clin Pathol 1999;52:241-244.
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| American Society of Hematology: Case Studies on anemia:www.ashteachingcases.org
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| National Institutes of Health: www.nlm.nih.gov/medlineplus/ency/article/000528.htm
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| E-Medicine: www.emedicine.com/med/topic1980.htmand....topic900.htm
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| Glucose-6-P dehydrogenase deficiency: www.rialto.com/g6pd/
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