Q1. Part 2. What will happen to an ATP molecule bound to a beta subunit in the T

Question

Q1.

Part 2. What will happen to an ATP molecule bound to a beta subunit in the T (tight) conformation when the gamma subunit rotates and causes the beta subunit to adopt the O (open) conformation?

Select ONE option:

A. The ATP molecule will be released.

B. The ATP molecule will be broken down to ADP and inorganic phosphate.

C. Nothing happens to either molecule yet.

Q2.

A single ATP synthase is capable of generating about 30 ATP molecules for every 100 protons that flow through its F0 complex. If we isolated a mutant ATP synthase in which one of its three beta-subunits could not bind ADP, how many ATP molecules would this mutant be expected to generate for every 100 protons that flow through it?

Select ONE option:

A. 30 ATP molecules

B. 20 ATP molecules

C. 10 ATP molecules

D. 0 ATP molecules

Q3.

To confirm Boyer’s “binding change model” for the ATP synthase, the F1 subunit was removed from the inner mitochondrial membrane and attached upside down to a glass slide (such that the ? and ? subunits were directly attached to the glass slide, and the ?-rotor was pointing straight up). A fluorescently-labeled actin filament was then attached to the ?-rotor to allow observation of its rotation in the microscope, as shown below. Prior to adding ATP, no movement was observed.

Part 1. Upon adding ATP, what result to do you expect?

Select ONE option:

1. No movement at all

2. Back and forth movement across 180 degrees

3. Rotation in 120 degree intervals

4. Rotation in 90 degree intervals

Part 2. Do you expect that the movement of the actin filament depends on the synthesis or the hydrolysis of ATP in this experiment?

Select ONE option:

1. hydrolysis of ATP

2. synthesis of ATP

3. cannot tell

Part 3. What do you expect to observe after a full cycle of the labelled actin filament, assuming each active site goes through the three binding states?

Select ONE option:

1. synthesis of one molecule of ATP

2. hydrolysis of one molecule of ATP

3. synthesis of three molecules of ATP

4. hydrolysis of three molecules of ATP

Q4.

Barth Syndrome is characterized by dysfunctional mitochondria with a lower capacity to produce ATP. Barth syndrome patients experience difficulty walking and exercising. Why do Barth patients have these impairments?

(Select all that apply.)

A. Because ATP is required for skeletal muscle contraction.

B. Because ATP is required for the pumping of blood by the heart.

C. Because ATP is required for the release of oxygen by red blood cells.

D. Because ATP is required for absorbing oxygen by red blood cells.

Q5.

The image below (Figure A) shows oxygen concentration plotted over time.

Figure A. Oxygen consumption over time.

What is the oxygen consumption rate in the oxygen consumption vs time plot shown in Figure A?

Select ONE option:

1. 1 micromole oxygen/min

2. 30 micromole oxgen/min

3. 100 micromole oxygen/min

4. 200 micromole oxygen/min

Q6.

The image below (Figure B) shows the plots of oxygen consumption from three different experiments, experiment A (green circles), experiment B (purple squares), and experiment C (orange triangles).

Figure B. Oxygen consumption vs time in experiments A, B, and C.

Which of the following correctly ranks the plots in Figure B from the highest to the lowest oxygen consumption rate?

Select ONE option:

1. A > B > C

2. B > C > A

3. C > B > A

Explanation / Answer

Q1. Part2: When ATP molecule is bound to a beta subunit in the T (tight) conformation and the gamma subunit rotates and causes the beta subunit to adopt the O (open) conformation, the ATP molecule is released from the ATP synthetase.

ANSWER: A. The ATP molecule will be released.

Q2. In beta subunit, ADT binds. So when there is mutation which results in no activity of beta subunit, ATP will not be produced.

ANSWER: D. 0 ATP molecules

Q3.

Part 1: The filament rotates in 3 evenly spaced angular substeps. So the angle of rotation for each substep is 120o (360o / 3)

ANSWER: 3. Rotation in 120 degree intervals

Part 2: In this experiment ATP is hydrolysed into ADP and phosphate. So the rotation depends on hydrolysis.

ANSWER: 1. hydrolysis of ATP

Part 3: Upon completion of one complete cycle either one molecule of ATP is produced or one molecule of ADP is produced. In this experiment, ATP is hydrolysed to produce ADP. So one molecule of ADP is produced at the end of each cycle.

ANSWER: 2. hydrolysis of one molecule of ATP

Q4: ATP is required for skeletal muscle contraction pumping of blood by the heart.

ANSWER: A. Because ATP is required for skeletal muscle contraction.

B. Because ATP is required for the pumping of blood by the heart.

Q5: Oxygen consumption rate is calculated from the slope as below:

Oxygen consumption rate = 30 micromolar / 30 min = 1 micromolar / min

ANSWER: 1. 1 micromole oxygen/min

Q6. Oxygen consumption rate of A = 0/10 = 0 micromolar / min

Oxygen consumption rate of B = 30/30 = 1 micromolar / min

Oxygen consumption rate of C = 100/20 = 5 micromolar / min

A<B<C

ANSWER: 3. C > B > A

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