Question

1. In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart muscle, the overall stoichiometry of the reaction requires 2 mol of cytochrome c per mole of QH2 because:

a. cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor.

b. cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor.

c. cytochrome c is water soluble and operates between the inner and outer mitochondrial membranes

d. heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much cytochrome c as QH2 for electron transfer to proceed normally.

e. two molecules of cytochrome c must first combine physically before they are catalytically active.

2. Which of the following statements about the chemiosmotic theory is correct?

a. Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane.

b. It predicts that oxidative phosphorylation can occur even in the absence of an intact inner mitochondrial membrane.

c. The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes.

d. The membrane ATP synthase has no significant role in the chemiosmotic theory.

e. All of the above are correct.

3. Uncoupling of mitochondrial oxidative phosphorylation:

a. allows continued mitochondrial ATP formation, but halts O2 consumption.

b. halts all mitochondrial metabolism.

c. halts mitochondrial ATP formation, but allows continued O2 consumption.

d. slows down the citric acid cycle.

e. slows the conversion of glucose to pyruvate by glycolysis.

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

a. create a pore in the inner mitochondrial membrane.

b. induce a conformational change in the ATP synthase.

c. generate the substrates (ADP and Pi) for the ATP synthase.

d. oxidize NADH to NAD+.

e. reduce O2 to H2O.

Answer 1

1. 2 mole of Cytochrome c is required per mole of QH2 as cytochrome is a one electron acceptor but QH2 is two electron donor.

The correct answer option is a.

2. Chemiosmotic theory is the theory that describes the electron transport chain.

The correct answer option is a.The electron transfer in mitochondria is accompanied....

3. Uncouplers of oxidative phosphorylation inhibit the formation of ATP but does not affect respiratory chain and ATP synthase.

The correct answer option is c.

4.The proton motive force that is generated by ETC will change the enzyme structure.

The correct answer option is b.