Study Questions for Exam 4

Study Question Set 22
Oxidative Phosphorylation


Chapter 19





Chapter 14





Chapter 19


11, 13 - 15, 19, 21, 23-27, 29, 30, 38



2, 3, 4

Additional Questions
  1. Explain why oxidation of glycerol-3-phosphate by mammalian mitochondria produces fewer ATPs than oxidation of NADH
  2. Give the reactions needed to transfer the reducing equivalents of cytosolic NADH into mitochondria in oxidizing liver cells.   Indicate the enzymes involved and all substrates and products for each enzymatic step.   Compare this shuttle mechanism to the mechanism for oxidizing cytosolic NADH in muscle.
  3. Explain why operation of the glycerol phosphate shuttle in muscle does not diminish the amount of dihydroxyacetone phosphate available for pyruvate formation.
  4. Account for the net stoichiometry of malate, aspartate, glutamate, and alpha-ketoglutarate during operation of the malate-aspartate shuttle in liver cells.
  5. Show each step that results in ATP formation in the pathways for aerobic catabolism of glucose to 6 CO2.   Account for the differences in ATP yield in mammalian liver compared to skeletal muscle.   (See table 19-5 in Lehninger.)
  6. Describe the general way in which the proton gradient across the inner mitochondrial membrane provides energy for the synthesis of ATP.
  7. Explain how protons entering the Fo base of the mitochondrial ATP synthase are able to cause rotation of the gamma subunit of the ATP synthase.   Be complete.
  8. Check out these internet links:
    • The University of Leeds has a nice presentation on the mitochondrial ATP synthase.   The site has a video from the classic experiment (described in Lehninger) that demonstrated that rotation of the gamma subunit is the probable link between proton movement across the membrane and ATP synthesis by the ATP synthase.   The video shows rotation of the gamma subunit when the isolated ATP synthase hydrolyzes ATP. Take a look at
    • The University of Leeds also has a nice tutorial on the respiratory chain and proton pumping stoichiometry for ATP synthesis at
Ox Phos questions from lecture 30:
  1. Describe the way in which the rotation of the gamma subunit of the ATP synthase causes the synthesis of ATP.   Be complete.
  2. Explain the nature of the energy-requiring step in the sequence of events whereby the ATP synthase "head" forms ATP.
  3. Explain why the stoichiometry of ATP formed / H+ moving through the ATP synthese depends on the number of c subunits on the "c-ring" of the Fo of the ATP synthase.
  4. In your opinion, is the ATP yield for oxidative phosphorylation using NADH as a substrate likely to turn out to be the same for all mitochondria?   Give reasons for your answer.
  5. Account for the NADH/H+ stoichiometry (as best we understand it) for electron transfer from NADH to oxygen in mammalian mitochondria:
    1. in general terms
    2. in terms of the specific stoichiometry for each "coupling site".   Account for any imbalances between protons removed from the matrix compared to protons released at the P side of the membrane for any coupling site where the issue arises.
  6. Explain what we mean by "Q cycle".
  7. Why is the lipid nature of ubiquinone (or other quinones) essential to the operation of a "Q loop"?
  8. Explain what we mean by the "QN" and "QP" sites in complex III of the mitochondrial electron transfer chain.   How do these two sites contribute to the unusual route of electron movement through complex III?
  9. Describe the recylcing of electrons throught the "Q cycle" in complex III that results in transport of 4 H+ into the intermembrane space of the mitochondrion (P side of the inner membrane) for each two electrons transferred from QH2 to cytochrome c.  

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