* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download BCHM 463 Supplemental Problems for Friday, April 9, 2004 1. a
Deoxyribozyme wikipedia , lookup
Metabolic network modelling wikipedia , lookup
Lactate dehydrogenase wikipedia , lookup
Photosynthesis wikipedia , lookup
Paracrine signalling wikipedia , lookup
Restriction enzyme wikipedia , lookup
Mitogen-activated protein kinase wikipedia , lookup
Proteolysis wikipedia , lookup
Microbial metabolism wikipedia , lookup
Butyric acid wikipedia , lookup
Lipid signaling wikipedia , lookup
Biochemical cascade wikipedia , lookup
Metalloprotein wikipedia , lookup
Nicotinamide adenine dinucleotide wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Biosynthesis wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Glyceroneogenesis wikipedia , lookup
Amino acid synthesis wikipedia , lookup
BCHM 463 Supplemental Problems for Friday, April 9, 2004 1. a) What is the net reaction for gluconeogenesis? 2 Pyruvate + 4 ATP + 2 GTP + 2 NADH + 4 H2O → Glucose + 4 ADP + 2 GDP + 6 Pi + 2 NAD+ + 2 H+ b) What is the net reaction for gluconeogenesis + glycolysis? 2 ATP + 4 H2O + 2 GTP → 2 ADP + 4 Pi + 2 GDP + 4 H+ 2. Which steps of the gluconeogenesis pathway are shared by enzymes in the glycolysis pathway? Steps 2, 4, 5, 6, 7, 8, and 9 Write out the four chemical reactions in gluconeogenesis that allow bypass of the three metabolically irreversible steps in glycolysis. Pyruvate carboxylase: Pyruvate + HCO3- + ATP → oxaloacetate + ADP + Pi + H+ Phosphoenolpyruvate carboxylase: Oxaloacetate + GTP → phosphoenolpyruvate + CO2 + GDP Fructose bisphosphatase: Fructose-1,6-bisphosphate + H2O → Fructose-6-phosphate + Pi Glucose-6-phosphatase: Glucose-6-phosphate + H2O → Glucose + Pi 3. What is the primary function of the pentose phosphate pathway? Produces NADPH 4. Write a balanced equation for the pentose phosphate pathway including structures of starting material and products. 3 G6P + 6 NADP+ + 3 H2O → 6 NADPH + 6 H+ + 3 CO2 + 2 F6P + GAP O O OPO3-2 O HO HO OH G6P OH O O -O P HO O O P -O O O N+ O OH NH2 N N N N OPO3-2 NH2 NH2 O O P -O HO O O P -O O O OH O N O HO OH OH NH2 N N F6P N N O HO OPO3 -2 HO OPO3-2 -2O PO 3 H OH NADP+ NADPH GAP BCHM 463 Supplemental Problems for Friday, April 9, 2004 5. What are the two key enzymes involved in glycogen metabolism and how are they regulated by phosphorylation? Glycogen synthase and glycogen phosphorylase (see Figs. 15-12 and 15-13 for detailed description of regulation through phosphorylation.) What is the effect of epinephrine on the regulation of these enzymes and how does this affect glycogen levels? Epinephrine starts a cascade of phosphorylation events which lead to breakdown of glycogen into Glucose1-phosphate for use in glycolysis. In other words, glycogen phosphorylase is phosphorylated and enters its “active” state. 6. Write the net reaction, including structures, of the two steps that produce NADPH in the pentose phosphate pathway. OPO3-2 OPO3-2 HO HO G6P DH O HO HO Mg++ OH OH O OH NADP+ CO2 NADPH 6-phosphogluconate dehydrogenase OH OH -2O PO 3 O - Mg++ 3PO OH O OH OH NADP+ OH OH -2O NADPH What is the significance of CO2 release in this pathway? This is a major driving force for the reaction. 7. Compare the relative efficiencies (in ATP’s per glucose oxidized) of glucose oxidation via glycolysis + the citric acid cycle vs. glucose oxidation via the pentose phosphate pathway + glycolysis. (Assume that NADH and NADPH are each equivalent to three ATPs and that FADH is equivalent to 2 ATPs.) Oxidation through glycolysis and the citric acid cycle yields ~38 ATP’s per molecule of glucose. The other pathway yields, assuming that it continues through the citric acid cycle, 37 ATPs per molecule of glucose. 8. Like glycolysis, the citric acid cycle is regulated by controlling the enzyme activities of 3 enzymes. a) Name these enzymes and give all species that inhibit (negatively modulate) the enzymes’ activities. Citrate synthase, isocitrate dehydrogenase, and ∝-ketoglutarate dehydrogenase are the control points for the citric acid cycle. See figure 16-14 for the intermediates and products which inhibit the citric acid cycle. BCHM 463 Supplemental Problems for Friday, April 9, 2004 b) Rationalize the use of these enzymes as control points (i.e. Why are these enzymes able to serve as control points?)? These enzymes function far from equilibrium (i.e. have large negative ∆G) and can therefore serve as control points for flux through this pathway. c) Are there other enzymes that might be able to serve as control points in the citric acid cycle? No, for all the other enzymes, ∆G is approximately 0. 9. Write a balanced equation for the citric acid cycle. 3 NAD+ + FAD + GDP + Pi + acetyl-CoA + 2 H2O → 3 NADH + FADH2 + GTP + CoA + 2 CO2 + 3 H+ 10. From which citric acid cycle intermediate are each of the following amino acids derived? a) aspartate: oxaloacetate b) glutamate: ∝-ketoglutarate