Kaplan FL 5 #30 Bio section

[akimhaneul]

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why is the proton gradient necessary for electrons to flow?

 

[theonlytycrane]

it drives ATP synthesis via ATP-synthase which is the point of the ETC.

 

[akimhaneul]

it drives ATP synthesis via ATP-synthase which is the point of the ETC.

I thought pushing electron through the etc was a favorable process that is pushing the hydrogens into inter membrane space. So why do you need the hydrogen gradient to push the electrons through the etc?


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[theonlytycrane]

I thought pushing electron through the etc was a favorable process that is pushing the hydrogens into inter membrane space. So why do you need the hydrogen gradient to push the electrons through the etc?


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As electrons flow through the ETC, a H+ gradient is formed in the inter-membrane space. If there's already a huge gradient built up, additional electron flow through the ETC would be unneeded until the gradient starts to dissipate.

 

[aldol16]

I thought pushing electron through the etc was a favorable process that is pushing the hydrogens into inter membrane space. So why do you need the hydrogen gradient to push the electrons through the etc?

Think of a pump working to pump water out of your basement. Initially, the pump works because the work it does is sufficient to increase the gravitational potential energy of the water. But once you pump more and more water outside, the gradient builds up. You can imagine this as the water that's already outside exerting a downward force on the water coming out of the pump until the pump can no longer overcome the force pushing down on it. Then the pump stops. This is why if you block ATP synthase, electron flow stops too - the protons can no longer get back into the mitochondria (and by design, the membrane is impermeable to protons). This is a key point - electron flow is coupled to ATP synthesis and vice versa.