Mitochondia confusion

[salemstein]

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I know for a fact poking a hole thru the inner membrane decreases ATP production, but how will it change O2 consumption and the transport of electrons, if at all?

 

[theonlytycrane]

ATP production is driven by the H+ gradient in the intermembrane space. With a hole, the gradient will be weaker resulting in less ATP production as you mentioned. O2 is the final electron acceptor at complex IV and electron transport powers the H+ gradient, so with less ATP production both in turn should also decrease.

 

[aldol16]

I know for a fact poking a hole thru the inner membrane decreases ATP production, but how will it change O2 consumption and the transport of electrons, if at all?

ATP production is driven by the H+ gradient in the intermembrane space. With a hole, the gradient will be weaker resulting in less ATP production as you mentioned. O2 is the final electron acceptor at complex IV and electron transport powers the H+ gradient, so with less ATP production both in turn should also decrease.

It won't decrease. It should increase O2 consumption and electron transport. This is because poking a hole in the membrane basically decouples proton transport from ATP synthesis and so the body will keep trying to pump more and more protons out since it's starving for ATP. Since O2 consumption is related to Complex IV, O2 consumption will increase and so will electron transport.

Think about it this way. You have a balloon and you're filling it with water. Before, you're filling it at some rate and the balloon is slightly permeable to water so it's leaking away at some rate. You'll reach equilibrium at some point where you're maintaining a steady level of water. Then, someone comes along and pokes a big hole in the balloon. Now, you're gonna need to pour water in at a higher rate to keep the water level steady. If you fail (i.e. are overwhelmed), then the balloon empties of water and deflates.

 

[theonlytycrane]

@aldol16

I guess I was assuming that the H+ gradient was rate-limiting for ATP synthesis. That is, in an equal snapshot of time less electron transport would occur and less O2 would be consumed even though it wanted to since the H+ gradient is hindered.

 

[aldol16]

I guess I was assuming that the H+ gradient was rate-limiting for ATP synthesis. That is, in an equal snapshot of time less electron transport would occur and less O2 would be consumed even though it wanted to since the H+ gradient is hindered.

But after uncoupling, ATP synthesis has nothing to do with it. The protons will just come right back in as Complexes I, III, and IV pump them out, making the complexes angrier and angrier so they want to work faster and faster. The point of uncoupling is to decouple proton transport from ATP synthesis so that they are no longer related to one another.

 

[theonlytycrane]

@aldol16 Just to clarify, uncoupling as in conceptually? Or biologically?

 

[aldol16]

@aldol16 Just to clarify, uncoupling as in conceptually? Or biologically?

Both. Biologically, proton transport is chemically coupled to ATP synthesis because the inner mitochondrial membrane is impermeable to protons so that protons can only enter through one pathway - i.e. through ATP synthase. But when you add an uncoupler, this punches holes in the membrane so that protons can enter via another pathway and thus are no longer coupled to ATP synthesis.