Question

1. In otherwise normal, intact (not leaky), coupled mitochondria supplied with succinate and ADP, if you add ANTIMYCIN:
   1. What happens to electron^- transport (works/stops)? Why?
   2. What happens to oxygen consumption (works/stops)? Why?
   3. What happens to proton pumping (works/stops)? Why?
   4. What happens to ATP synthesis (works/stops)? Why?

Answer 1

Succinate enters in to the ETC at complex II ( sucvinate CO Q dehydrogenase) level. Antimycin is complex III inhibitor ( cytochrome reductase) . Based on this information we can solve the questions

A) ETC will stop after treatment, as this compound inhibits complex III so it prevents the flow of electrons through the chain .

B) oxygen consumption will also decrease. Due to inhibition of complex III there will be no movement of electrons through the chain so they will be not able to reach at complex IV ( site where oxygen is utilized). At complex IV , these electrons meet with or combine with oxygen and H and form water thus utilize oxygen. In presence of antimycin, as ETC is inhibited due to no transport of electrons, oxygen molecules will net be utilized so oxygen consumption will be decreased.

C) proton pumping will also decreased.

Protin pumping is also associated with transport of electrons, so image to inhibition of electrons transport chain proton will not be transported in to intermembrane space.

D) accumulated H will generate proton motive force ( PMF), which is responsible for generation of ATP using ATP synthase. So in absence of H ion in intermembrane space ATP synthesis will also stop.