Exam 19: Oxidative Phosphorylation and Photophosphorylation

A recently discovered bacterium carries out ATP synthesis coupled to the flow of electrons through a chain of carriers to some electron acceptor. The components of its electron transfer chain differ from those found in mitochondria; they are listed below with their standard reduction potentials. (a) Place the electron carriers in the order in which they are most likely to act in carrying electrons. (b) Is it likely that O₂ (for which E'° = 0.82 V) is the final electron acceptor in this organism? Why or why not? (c) How would you calculate the maximum number of ATP molecules that could theoretically be synthesized, under standard conditions, per pair of electrons transfered through this chain of carriers? (The Faraday constant, , is 96.48 kJ/V · mol.) $\Delta$ G'° for ATP synthesis is +30.5 kJ/mol.

The compound 2,4-dinitrophenol (DNP), an uncoupler, was briefly used as a weight-loss drug. Some of its effects in people who took the drug included weight loss and higher than normal body temperature. Some people even died. Explain the first two effects of the compound in biochemical terms.

What is the role of cytochrome c in apoptosis?

How many molecules of water are produced by the electron-transport chain during the complete aerobic oxidation of one molecule of pyruvate?

Which statement explains why the [ATP]/[ADP][P_i] ratio is relatively stable in a cell?

During the operation of the malate-aspartate shuttle, what process does NOT occur?

Bovine ATP synthase contains 8 c subunits while yeast ATP synthase contains 10 c subunits. How many protons would be needed for each ATP in these two synthases, and how would it impact the P:O ratio?

Diagram the path of electron flow from NADH to the final electron acceptor during electron transport in mitochondria. For each electron carrier, indicate whether only electrons, or both electrons and protons, are accepted/donated by that carrier. Also, indicate where electrons from succinate oxidation enter the chain of carriers.

During oxidative phosphorylation, the proton motive force (electrochemical gradient) that is generated by electron transport is used to:

Mammals produce heat by using which endogenous uncoupling agent?

During oxidative phosphorylation, the proton motive force that is generated by electron transport is used to:

Almost all of the oxygen (O₂) one consumes in breathing is converted to:

Under standard conditions, NADH reoxidation by the electron-transport chain has a free-energy change equal to -220 kJ/mol. With 100% efficiency, how many ATP could be synthesized under standard conditions? What is the "actual" efficiency given these numbers?

Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation. Which statement CORRECTLY describes the mode of action of the three inhibitors?

Mutations in mitochondrial genes frequently produce diseases that affect the brain and skeletal muscle (mitochondrial encephalomyopathies). Why are these two tissues particularly sensitive to mitochondrial mutations?

If a drug that specifically prevented the interaction of cytochrome c with other proteins was added to respiring mitochondria in a test tube, what effects would be observed?