Deoxynucleotides (deoxynucleoside triphosphates) are the substrates for DNA synthesis. Calculate the number of glucose molecules that must be degraded to generate the energy required for the synthesis of 1000 deoxynucleotides used in DNA synthesis. Assume that glucose is oxidized completely to CO2 and H2O, the malate–aspartate shuttle is in operation, and NADPH is the equivalent of 4 ATP

Deoxynucleotides (deoxynucleoside triphosphates) are the substrates for DNA synthesis. Calculate the number of glucose molecules that must be degraded to generate the energy required for the synthesis of 1000 deoxynucleotides used in DNA synthesis. Assume that glucose is oxidized completely to CO2 and H2O, the malate–aspartate shuttle is in operation, and NADPH is the equivalent of 4 ATP

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter27: Metabolic Integration And Organ Specialization

Section: Chapter Questions

Problem 20P: Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy...

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The enzyme phosphofructokinase (PFK) catalyzes the reaction fuctose 6 phosphate and ATP, functions as a tetramer and is regulated by several mechanisms, including allosteric regulation. Based on your knowledge of the homotropic regulation of PFK, draw a curve of the rate of Fructose 1, 6-bisphosphate produced vs. [ATP].
During glycogen synthesis, glucose-1P is converted into a molecule called UDPG. This reaction also cleaves uridine triphosphate (UTP) forming uridine monophosphate and pyrophosphate (PPi). Provide four reasons why UTP can be used to power this reaction (no diagrams necessary).
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The glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconcogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP] and [Pi] =1 mM. Consider the following glycolytic reaction catalyzed by hexokinase: ATP + glucose = AG' = -16.7 kJ/mol ADP + glucose-6-phosphate (a) Calculate the equilibrium constant (K) for this reaction at 298 K, and from that, calculate the maximum [glucose-6-phosphate]/[glucose] ratio that would exist under conditions where the reaction is still thermody- namically favorable. (b) The reverse of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H,0 = glucose + P, AGr = -13.8 kJ/mol K= 262 for this reaction. Calculate the maximum ratio of [glucose]/ [glucose-6-phosphate] that would exist under conditions where the reaction is still thermodynamically favorable. (c) Under what cellular conditions would both directions in the…
ATP is an ALLOSTERIC INHIBITOR of the phosphofructokinase enzyme, which is a key catalyst for one of the first steps of Glycolysis. Citrate (citric acid) is a 6-carbon product of the first reaction of the Krebs Cycle (aka Citric Acid Cycle). Interestingly, Citrate enhances the inhibitory effect of ATP on phosphofructokinase. What is a likely explanation for the inhibitory effects of these molecules? Excess ATP and Citrate signal the cell that Glycolysis should be speeded up. Excess ATP and Citrate signal a positive feedback loop. Excess ATP and Citrate signal the cell that Glycolysis should be slowed. Excess ATP and Citrate compete for the active site of phosphofructokinase.
Imagine a triglyceride comprised of (3) saturated C12 fatty acids. Calculate the number of ATP generated from the complete oxidation of one of these 12-carbon fatty acids to CO2 and water in the liver. Assume that each NADH = 2.5 ATP and each FADH2 = ETC generates 1.5 ATP. Any step that yields pyrophosphate as a product should be treated as an input (i.e. net loss) of (2) ATP.
The glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconeogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP]; [P;] = 1 mM. Consider the glycolytic reaction catalyzed by hexokinase: ATP + glucose ADP + glucose-6-phosphate AG = - 16.7 kJ/mol (a) Calculate the equilibrium constant (K) for this reaction at 298°K, and from that, calculate the maximum [glucose-6-phosphate]/ Iglucose] ratio that would exist under conditions where the reaction is still thermodynamically favorable. (b) Reversal of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H20 = glucose + P AG" = -13.8 kJ/mol
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Complete the sentence describing the pentose phosphate pathway in cells that require much more ribose 5-phosphate than NADPH. These cells need ribose 5-phosphate but have relatively higher concentrations of NADPH and lower concentrations of NADP*. Choose from the listed words to fill in the blanks: xylulose 5-phosphate, fructose 6-phosphate, glucose 6-phosphate, five, two, three, glyceraldehyde 3- phosphate, erythrose 4-phosphate, sedoheptulose 7-phosphate. One molecule of and two molecules of are used to generate molecules of ribose 5-phosphate by the reverse reactions of the nonoxidative phase of the pentose phosphate pathway.
Explain the purpose of the glycerol 3 phosphate shuttle (Don’t worry about the mechanism, just the purpose of the shuttle. Just one sentence here!). Suppose a cell could only rely on the glycerol 3 phosphate shuttle and not the malate-aspartate shuttle, how would that affect the amount of ATP that could be generated from the complete oxidation of 1 molecule of glucose in that cell? How would this change the amount of ATP that could be generated from the complete oxidation of 1 molecule of palmitate in this cell?
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