You decide to compare the rate of oxygen consumption by purified mitochondria fr

Question

You decide to compare the rate of oxygen consumption by purified mitochondria from the patient and from a healthy individual. In your experiment, you add to the preparation of mitochondria a combination of substrates followed by the addition of ADP. The addition of substrates is necessary, because the purification of mitochondria results in a near depletion of substrates. It limits the production of ATP and the consumption of oxygen unless a few essential substrates are added to "recharge" mitochondria. 1) In experiment #1, you add glutamate and malate followed by the addition of ADP. In mitochondria, glutamate can be converted to a-ketoglutarate, a reaction coupled with NAD reduction. Furthermore, transporters in the inner membrane of mitochondria favor the import of malate and glutamate inside the mitochondrial matrix and the export of aspartate and ? ketoglutarate outside mitochondria. The following figure shows three possible profiles (A, B & C) for the consumption of oxygen. Glutamate Aspartate Glutamate Glutamate Aspartate ADP ADP ADP Time Profile A Time Profile B Time Profile C Complete the following sentence (1 attempt) Oxygen consumption for the patient's mitochondria corresponds to profile A/B/C while oxygen consumption for the healthy individual's mitochondria correspond to profile A/B/C 2) In experiment #2, you add succinate and rotenone followed by the addition of ADP. Rotenone blocks the transfer of electron from complex I to ubiquinol (Coenzyme Q) What following statements are correct? Briefly explain A. Electrons donated by succinate are not transferred to complex III B. Electrons donated by succinate are transferred to complex III C. The oxidation of succinate is coupled with the reduction of NAD D. The oxidation of succinate is coupled with the reduction of FAD E. The addition of a drug blocking the citric acid cycle would affect the results of experiment #2 F. The oxygen consumption profiles for the patient's mitochondria are identical in experiments #1 and #2

Explanation / Answer

1) as glutamate is added, it serves as the substrate which generate reduced NAD, and electrons are transferred to oxygen,through electron transport chain(ETC). then addition of ADP causes a sudden burst of oxygen uptake as the ADP is converted into ATP and oxygen concentration decreases.

hence profile B is correct for healthy individual.

Now,as the type of disorder or where does it affect in the electron transport chain is not mentioned, let us assume the diffect is in the complex 1 in electron transport chain hence the electron taken from the oxidation of NAD is unable to be transferred to oxygen. and correspondingly ATP production is disabled. so the patient is suffering from less energy production. hence after addition of ADP no consumption of oxygen increases.

so the correct profile for patient will be A

2) succinate coverted to fumarate and produces reduced FAD, which is oxidised by complex 2 of ETC and elctrons are transferred to coenzymeQ. as the rotenone block only electron transfer from complex 1 but not from complex 2, it has no effect in healthy indivisual.

but if citric acid cycle inhibitor is added then succinate will not be transferred to fumarate and reduced FAD will not form. hence the result of experiment will be different.

but in patient as the electron transport occurs from complex 2 so the ATP prduction will occur and profile will be different from experiment 1.

so the option B , D, E are correct.

3) when TMPD and ascorbate is added, it reduces the cytochrome c. hence for both of patient and indivisual, after addtion of ADP oxygen comsumption increases.

cytochrome c is a part of complex 3, hence the electrons are able to be trnsported to oxygen.

so option B, D, F are correct.

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