Consider the malate dehydrogenase reaction, part of tricarboxylic acid cycle, shown below. malate + NAD+ <==> oxaloacetate + NADH + H+ ΔGo’ = 29.7 kJ/mol It has been reported (Wheeler and Mathews (2012) J. Biol. Chem. 887, 31218-31222) that the concentrations of NAD+ and NADH in yeast mitochondria were 20 mM and 0.3 mM, respectively. If we performed similar measurements and also determined that the concentration of malate in yeast mitochondria was 0.5 mM and that of oxaloacetate was 0.1 µM at pH 7.0 at 37˚C, use this information to address the following. Calculate the equilibrium constant for the given reaction. Calculate the free energy of the reaction in yeast mitochondria. Assign each reaction (the one under standard conditions and the one in yeast mitochondria) as being exergonic or endergonic. Explain your reasoning. When comparing the free energy values for standard conditions and the conditions in yeast mitochondria describe the relationship between the equilibrium constant (K) and the reaction quotient (Q) (i.e., is Q = K, Q > K, or Q < K?) and provide the basis for your answer.
Electron Transport Chain
The electron transport chain, also known as the electron transport system, is a group of proteins that transfer electrons through a membrane within mitochondria to create a gradient of protons that drives adenosine triphosphate (ATP)synthesis. The cell uses ATP as an energy source for metabolic processes and cellular functions. ETC involves series of reactions that convert redox energy from NADH (nicotinamide adenine dinucleotide (NAD) + hydrogen (H)) and FADH2(flavin adenine dinucleotide (FAD)) oxidation into proton-motive force(PMF), which is then used to synthesize ATP through conformational changes in the ATP synthase complex, a process known as oxidative phosphorylation.
Metabolism
Picture a campfire. It keeps the body warm on a cold night and provides light. To ensure that the fire keeps burning, fuel needs to be added(pieces of wood in this case). When a small piece is added, the fire burns bright for a bit and then dies down unless more wood is added. But, if too many pieces are placed at a time, the fire escalates and burns for a longer time, without actually burning away all the pieces that have been added. Many of them, especially the larger chunks or damp pieces, remain unburnt.
Cellular Respiration
Cellular respiration is the cellular process involved in the generation of adenosine triphosphate (ATP) molecules from the organic nutritional source obtained from the diet. It is a universal process observed in all types of life forms. The glucose (chemical formula C6H12O6) molecules are the preferred raw material for cell respiration as it possesses a simple structure and is highly efficient in nature.
Consider the malate dehydrogenase reaction, part of tricarboxylic acid cycle,
shown below.
malate + NAD+ <==> oxaloacetate + NADH + H+ ΔGo’ = 29.7 kJ/mol
It has been reported (Wheeler and Mathews (2012) J. Biol. Chem. 887, 31218-31222) that the
concentrations of NAD+ and NADH in yeast mitochondria were 20 mM and 0.3 mM,
respectively. If we performed similar measurements and also determined that the concentration
of malate in yeast mitochondria was 0.5 mM and that of oxaloacetate was 0.1 µM at pH 7.0 at
37˚C, use this information to address the following.
Calculate the equilibrium constant for the given reaction.
Calculate the free energy of the reaction in yeast mitochondria.
Assign each reaction (the one under standard conditions and the one in yeast
mitochondria) as being exergonic or endergonic. Explain your reasoning.
When comparing the free energy values for standard conditions and the conditions
in yeast mitochondria describe the relationship between the equilibrium constant (K) and the
reaction quotient (Q) (i.e., is Q = K, Q > K, or Q < K?) and provide the basis for your answer.
Given the standard reduction potentials (Eo’) for ubiquinone (Q) and NADP+
provided below, consider the following questions.
Q + 2H+ + 2e- ---> QH2 Eo’ = 0.04 V
NADP+ + H+ + 2e- ---> NADPH Eo’ = -0.32 V
Calculate the standard ΔEo’ for the oxidation of NADPH by Q. From the reactants
in your derived
Calculate the standard free energy of the redox reaction in part (a) and indicate if the
reaction is exergonic or endergonic.
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