Question

Q2.

The release of ATP by the beta subunit is most directly dependent on:

Select ONE option:

1. the flow of protons from the intermembrane space to the matrix.

2. the rotation of the c-ring in the membrane.

3. the passage of electrons along the electron transport chain.

4. a conformational change in the beta subunit.

Q3.

What defines the direction of rotation of the c-ring in the F0 complex?

(Select ALL that apply.)

1. Amino acids side chains in c-subunits will repel a bound proton if the c-ring rotates in the wrong direction

2. The availability of ADP and inorganic phosphate as substrates

3. The direction of the proton gradient relative to the inner mitochondrial membrane

4. The conformational changes in the alpha and beta subunits

Q4.

The release of protons by the c-ring is more favorable on the matrix side of the membrane because:

Select ONE option:

1. of the lower concentration of protons on the matrix side.

2. of the rotation of the c-ring.

3. ATP is synthesized on the matrix side.

4. the citric acid cycle enzymes are on the matrix side.

Q5.

By which of the following mechanisms could ATP synthesis potentially be inhibited?

(Select ALL that apply.)

A. By dissociating the F1 complex from the F0 complex

B. By blocking proton passage through the F0 complex

C. By blocking the rotation of the ?3?3 hexamer of the F1 complex

D. By blocking inorganic phosphate from binding to the F1 complex

Q6.

What would happen to the mitochondrial proton gradient, mitochondrial respiration (mitochondrial oxygen consumption), and the NADH oxidation rate in cells treated with carbonyl cyanide-4-trifluoromethoxyphenylhydrazone (FCCP), a molecule that increases the permeability of the inner mitochondrial membrane to protons?

Part 1. The mitochondrial proton gradient would:

Select ONE option:

1. increase

2. decrease

Part 2. Mitochondrial respiration (mitochondrial oxygen consumption) would:

Select ONE option:

1. increase

2. decrease

Part 3. The NADH oxidation rate would:

Select ONE option:

1. increase

2. decrease

Q7.

Bongkrekic acid is a mitochondrial toxin produced by bacteria in fermented coconuts. It blocks the inner membrane protein responsible for transporting ATP from the mitochondrial matrix to the cytosol. Bongkrekic acid also inhibits ADP import from the cytosol into the matrix for phosphorylation. Which of the following will occur in a cell exposed to bongkrekic acid?

(Select all that apply.)

A. Most ATP in the cell will be produced by glycolysis because the mitochondria are inhibited.

B. The mitochondrial membrane potential will decrease due to decreased ETC proton pumping.

C. Respiration will decrease because the ATP synthase will lack ADP as the reactant.

D. Mitochondrial ATP levels will decrease.

Q8.

Experiment 1. Two sets of cells are subjected to a FRAP experiment. One cell has a lipid bilayer that includes cholesterol, which makes it less fluid; and the other cell has a membrane made purely of phospholipids. The results are shown below. Which curve, A or B, was obtained from cells with a membrane that includes cholesterol?

% initial fluorescence % initial fluorescence 2

Select ONE option:

1. A

2. B

Experiment 2. Membrane fluidity decreases as the temperature cools. If you conducted two FRAP experiments with the same cell, one experiment at warm temperature, and the other at a cooler temperature, which of the FRAP curves below best represents the cell at the warmer temperature?

Select ONE option:

1. A

2. B

Answer 1

Please find the answers below:

Answer 2: Choice 1 (The onset of chemiosmosis across the mitochondrial matrix is mandatory for ATPase to generate ATP)

Answer 3: Choices 1, 3 (The structural complexity of the complex V in the electron transport chain is maintained by a specific orientation and composition of unique amino acids which regulate the conformational movement of the hexamer of alpha and beta subunits. Further, the direction of the proton gradient also regulates the synthesis of ATP at the complex V)

Answer 4: Choice 1 (Since the proton-motive force works according to chemiosmotic principle, the movement of protons would take place on the matrix side since it lacks total protons as compared to the periphery)

Answer 5: Choices 1, 3 (The structural integrity of the F0-F1 complex is extremely necessary for the functioning of complex V, disintegration of which causes absolute loss in ATP generation. Further, the hexameric complex of alpha and beta subunits arranged in a particular 3-dimensional orientation is also mandatory for the movement of this complex, hence ATP generation.)