Q1. You recently identified a new compound, TX32, present in e-cigarette vapor t

Question

Q1.

You recently identified a new compound, TX32, present in e-cigarette vapor that you suspect causes mitochondrial dysfunction. Your preliminary data from Part 1 indicated that TX32 reduces mitochondrial membrane potential in a dose-dependent manner. However, you do not know whether membrane potential is reduced due to:

1. decreased proton pumping, or

2. increased proton leakage.

PART 1: If option 1 (decreased proton pumping) is correct, you expect TX32 will -------------------- mitochondrial oxygen consumption independent of whether ATP is synthesized.

Select ONE option for the blank:

1. increase

2. decrease

PART 2: If option 2 (increased proton leakage) is correct, you expect TX32 will --------- mitochondria oxygen consumption independent of whether ATP is synthesised.

Select ONE option for the blank:

1. increase

2. decrease

Q2.

You prepare two culture dishes with cells. You treat one with TX32 and leave the other untreated.

The following day, you isolate mitochondria from the untreated dish. You begin recording oxygen concentration in the sealed respiration chamber and then sequentially add pyruvate, in order to fuel the proton pumps, and ADP, in order to initiate ATP synthesis.

PART 1: Which region of the graph of the untreated samples indicates oxygen consumption that is directly tied to the phosphorylation of ADP to ATP?

Select ONE option:

1. The region immediately following mitochondria addition before pyruvate addition

2. The region immediately following pyruvate addition before ADP addition

3. The region immediately following ADP addition

PART 2: Which region of the graph indicates oxygen consumption that is independent of the phosphorylation of ADP to ATP?

Select ONE option:

1. The region immediately following mitochondria addition before pyruvate addition

2. The region immediately following pyruvate addition before ADP addition

3. The region immediately following ADP addition

Q3.

Next, you repeat the experiment in TX-32 treated cells and obtain the following results.

Based on these data, what is the most likely mechanism by which TX32 reduces mitochondrial membrane potential?

Select ONE option:

1. TX32 inhibits proton pumping activity since oxygen consumption is further decreased in treated cells.

2. TX32 increases proton leakage through the membrane since oxygen consumption is increased in treated cells independent of ATP synthesis.

Explanation / Answer

Q1. You recently identified a new compound, TX32, present in e-cigarette vapor t

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