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Question:
In actively respiring liver mitochondria, the pH in the matrix is about half a pH unit
higher than it is in the cytosol. Assuming that the cytosol is at pH 7 and the matrix is a
sphere with a diameter of 1 μm [V = (4/3) πr3], calculate the total number of protons in
the matrix of a respiring liver mitochondrion. If the matrix began at pH 7 (equal to that
in the cytosol), how many protons would have to be pumped out to establish a matrix
pH of 7.5 (a difference of 0.5 pH unit)?
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QUESTION:
Heart muscle gets most of the ATP needed to power its continual con- tractions through oxidative phosphorylation. When
oxidizing glucose to CO2, heart muscle consumes O2 at a rate of 10 μmol/min per g of tissue, to replace the ATP used in
contraction and give a steady-state ATP concentration of 5 μmol/g of tissue. At this rate, how many seconds would it take
the heart to consume an amount of ATP equal to its steady-state levels? (Complete oxidation of one molecule of glucose to
CO2 yields 30 ATP, 26 of which are derived by oxidative phosphorylation using the 12 pairs of electrons captured in the
electron carriers NADH and FADH2.)
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