The enzyme malate dehydrogenase catalyzes the conversion of malate to oxaloacetate in the final step that completes the Citric Acid Cycle. The AG' of this reaction is +29.7 kJ/mol. Explain how this thermodynamically unfavorable reaction could possibly be accomplished by the cell even though the reaction is not coupled to a favorable reaction.

The enzyme malate dehydrogenase catalyzes the conversion of malate to oxaloacetate in the final step that completes the Citric Acid Cycle. The AG' of this reaction is +29.7 kJ/mol. Explain how this thermodynamically unfavorable reaction could possibly be accomplished by the cell even though the reaction is not coupled to a favorable reaction.

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter18: Glycolysis

Section: Chapter Questions

Problem 24P: Based on your knowledge of the structure of NAD+ and an assumption that coenzyme dissociation is the...

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The enzyme malate dehydrogenase catalyzes the conversion of malate to oxaloacetate in the final step that completes the Citric Acid Cycle. The ∆G of this reaction is +29.7 kJ/mol. Explain how this thermodynamically unfavorable reaction could possibly be accomplished by the cell even though the reaction is not coupled to a favorable reaction.
The complete combustion of palmitate and glucose yields 9781 kJ ∙ mol−1 and 2850 kJ ∙ mol−1 of free energy, respectively. Compare these values to the free energy (as ATP) obtained though catabolism of palmitate and glucose under standard conditions. Which process is more efficient?
Which reaction in the citric acid cycle is most analogous to the oxidative decarboxylation of 6- phosphogluconate to ribulose 5-phosphate? What kind of enzymebound intermediate is formed in both reactions?
If palmitic acid is subjected to complete combustion in a bomb calorimeter, one can calculate a standard free energy of combustion of 9788 kJ/mol. From the ATP yield of palmitate oxidation, what is the metabolic efficiency of the biological oxidation, in terms of kilojoules saved as ATP per kilojoule released? (Ignore the cost of fatty acid activation.)
The citric acid cycle itself, which is composed of enzymatically catalyzed steps, can be thought of essentially as a supramolecular enzyme. Explain.
Using the following glycolisis diagram, a. name all the steps in citric acid cycle, what are the intermediates. refer to the diagram given. b. Is glycolysis endothermic or exothermic.
Hexokinase catalyzes the first step of glycolysis, in which glucose is phosphorylated to form glucose‑6‑phosphate. Give two reasons why a Mg2+ cation is required to facilitate this reaction.
How many total (NOT NET) molecules of ATP are synthesized from ADP via glycolysis of a single molecule of glucose? Explain by detailing the reactions (steps) involved.
Consider one of the reactions of the citric acid cycle shown below Malate + NAD+ ⇆ Oxaloacetate + NADH + H+ (malate dehydrogenase) ΔG˚′ = +29.7 kJ/mol. Describe two factors that allow this thermodynamically unfavorable reaction to occur in the direction of malate to oxaloacetate.
If the hydrolysis of 1 M glucose 6-phosphate catalyzed by glucose 6-phosphatase has a ΔG′∘ of −11.386 kJ/mol at 25 °C, what percentage of substrate remains once the reaction reaches equilibrium assuming no product was initially present? (Round answer to the nearest whole number)
The citric acid cycle operates only when O2 is present, yet O2 is not a substrate for the cycle. Explain.
The ΔG°’ for the aldolase reaction of glycolysis in muscle is +22.8 kJ/mol. Why does the aldolase reaction proceed in the direction of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate during glycolysis?