You isolate intact mitochondria and equilibrate them in a buffered solution at pH 9, containing 0.1 M KCl and ADP plus Pi, but without succinate (no citric acid cycle and no proton pumps). You collect by centrifugation, and quickly resuspend them in a new buffer at pH 7, without KCl, but with valinomycin (a hydrophobic, K+ ionophore). Note: The K+ rushing out will create a huge positive charge differential. What do you predict will be the result on the oxygen consumption and the production of ATP? Explain. Include what is happening to all the solutes present. Think about charge gradients as well as solute gradients. The figure. above shows the initial conditions of the mitochondria after is has been transferred from the pH 9 to the pH 7 solution.
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The mitochondria are initially in a high pH (alkaline) environment with a high concentration of K+ ions. Show more…
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Sri K.
In an experiment, a scientist isolates mitochondria from living cells and suspends them in two different buffered solutions. One solution is maintained at pH 4, while the other solution is maintained at pH 9. The scientist finds that mitochondria in the solution at pH 4 continue to produce ATP, but those in the pH 9 solution do not. The results of the experiment can be used as evidence in support of which of the following scientific claims about mitochondrial activity? A. Mitochondria in a cell-free environment are unable to convert thermal energy into ATP. B. The electron transport chain pumps electrons from the cytosol to the mitochondrial matrix. C. ATP production in mitochondria requires a hydrogen ion gradient that favors the movement of protons into the mitochondrial matrix. D. ATP synthase molecules change their orientation in relation to the proton gradient across the mitochondrial membrane.
Jakob W.
Mitochondria harness the proton gradient across the inner membrane to generate ATP. The pH gradient generates a membrane potential of -60 mV. The synthesis of one molecule of ATP requires 3 protons to pass through the F0/F1 ATPase. If the ATP/ADP ratio in the matrix is 1:5, the Pi concentration is 2 mM, and the matrix pH is 7.0, what must the pH be in the space to generate one molecule of ATP at 37°C? ΔG° = 7.3 kcal/mol for ATP synthesis.
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