You have isolated intact mitochondria from cardiac tissue. Assume all proteins a

Question

You have isolated intact mitochondria from cardiac tissue. Assume all proteins and cofactors (ADP, P, NAD+, FAD etc.) necessary for electron transport and oxidative phosphorylation are present in excess. You divide a solution of the mitochondria into two test tubes. To the solution in one tube you add Rotenone* (System 1), to the solution in the other tube you add aurovertin* (System 2). To each tube you then add an oxidizable substrate (e.g. pyruvate; assume the citric acid cycle is operational) and measure O2 uptake by means of an oxygen electrode) a) Is oxygen consumed in System 1? Briefly explain. b) If the pH of the solution of System 1 is decreased, will ATP be produced? Explain. c) If the pH of the solution of System 1 is increased, will O2 be consumed? Explain. d) Within a few minutes of adding all the components described above, oxygen consumption in System 2 decreases dramatically. Briefly explain this observation. e) What could you add to System 2 to restore oxygen consumption? (assume aurovertin remains bound to ATP synthase). Explain. *note: rotenone inhibits Complex I and aurovertin inhibits ATP synthase

Explanation / Answer

1. Oxygen is unable to consume because rotenone prevent the availability of oxygen and transport of electron in mitochondria by blocking ubiquitone reductase.

2. While formation of proton gradient acidic conditions are generated. Decreasing the pH will generate stronger proton gradgrad fevouring ATP production.

3. Increase in pH will oxidise Rotenone to Rotenolone which will decrease toxicity and increase oxygen consumption.

4.aurovertin is the inhibitor of oxidative phosphorylation and stops the precess by binding at b subunit of ATPase.

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