1. When actively respiring mitochondria are treated with the drug myxothiazole (

Question

1. When actively respiring mitochondria are treated with the drug        myxothiazole (shown below), the ratio of the cytochrome c1            (Fe3+)/cytochrome c1 (Fe2+) and the ratio of cytochrome bL        (Fe3+)/cytochrome bL (Fe2+) both increase. What does this tell you about the site of action of this drug (1 point)?

2. The Fe/S complex in Complex III donates an electron to a cytochrome c1. The two relevant reduction reactions with the corresponding reduction             potentials are shown below.

                        Fe/S (ox) + e- -----> Fe/S (red)                                    Eo’       = 0.280 V

                        cytochrome c1 (ox) + e- -----> cytochrome c1 (red)    Eo’       = 0.215 V

                        Calculate the standard free energy change (Go’) for this process. Remember that Go’ = - n F Eo’, where F is 96.5 kJ V-1 mol-1

Explanation / Answer

Go’ = - n F Eo’, where F is 96.5 kJ V-1 mol-1

Fe/S (ox) + e- -----> Fe/S (red)                                    Eo’       = 0.280   

cytochrome c1 (ox) + e- -----> cytochrome c1 (red)    Eo’       = 0.215 V

E0 cell = E0 red -E0 oxd

            = 0.28-0.215 = 0.065V

Go’ = - n F Eo

          = -2*96500*0.065 = -12545J

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