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Unformatted text preview: Carbohydrate Practice Problems These lectures are spread over several chapters: Chapter Reading Problems Chapter 11 11.1 and 11.2 (pp. 324-325) #12 and 14 Chapter 20 20.3, 20.4, and 20.5 (pp. 590-591) #10 Chapter 16 16.3 and 16.4 (pp. 473-474) # 9 (b,c), 10, and 16 Chapter 21 all (pp. 615-616) 2, 3, 4, 7, 9, 10, 11 (a, c, d, and e), 12 1. Use your knowledge of biochemistry to explain why surculose tastes sweeter than sugar and yet has "no calories." 2. Pure cellulose is tough, fibrous and insoluble in water. Glycogen isolated from liver, which has a comparable molecule weight, is soluble in water. What are the biological advantages to each molecule's physical properties? The polysaccharides have some similarities: both are polymers of D-glucose connected by (1->4) linkages. What structural features of the two molecules explain the observed physical differences? 3. What explains the observation that people born with a deficiency in the enzyme glucose 6-phosphate dehydrogenase become clinically anemic if they have a diet rich in fava beans? 4. Why does starvation lead to loss of muscle mass? 5. Gluconeogenesis and glycolysis are opposing pathways. In what way(s) are they similar and in what way(s) are they different? 6. Avidin, a protein found in egg whites, binds to biotin so tightly that it inhibits enzymes that require biotin. The enzyme pyruvate carboxylase, which catalyzes the conversion of pyruvate to oxaloacetate using biotin as a coenzyme. How will high concentrations of avidin affect gluconeogenesis? Is there a way around this effect? 7. Fructose 1,6 bisphosphatase catalyzes the hydrolysis of fructose 1,6 bisphosphate to form fructose 6 phosphate during gluconeogenesis. Explain why the congenital disease fructose 1,6 bisphosphatase deficiency results in high levels of blood lactate. 8. Explain the four cellular fates of glucose 6-phosphate (including the pathways involved). Give one example of how the metabolic fate of this molecule is determined. 9. Why do glucose molecules produced by the glycogen phosphorylase reaction yield more ATP than dietary glucose? How many more ATPs? 10. What effect does protein kinase A (PKA) activation have on glycogen metabolism with respect to glycogen synthase and glycogen phosphorylase activities? Does PKA activation increase or decrease the amount of stored glycogen in the body? ...
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- Spring '07