Mutation to ATP synthase?

[TheGoodLife570]

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You have identified a mutation in the c subunit in the ATP synthase. The mutation changes the glutamate residue, (that facilitates proton pumping into the mitochondrial matrix), to a glycine. The inability to dissipate the proton gradient will have which of the following impacts on the electron transport chain?

-decreased ATP synthesis

-increased ATP synthesis

-increased NADH oxidation

-increased oxygen consumption

A answer I found online stated that it would increase ATP synthesis. Can someone explain the reasoning or the correct answer?

Thanks

 

[theonlytycrane]

Due to the mutation, the proton gradient (which drives ATP synthesis) is not being dissipated. As a result, ATP synthesis will decrease.

NADH gets oxidized to NAD+ when it drops off electrons at complex I to pump protons into the intermembrane space. If this space is already full of protons, continued H+ pumping into this space won't be favored. And oxygen is the final electron acceptor in the chain at complex IV. Electrons won't be flowing through the chain if the H+ gradient is stuck.

 

[aldol16]

A answer I found online stated that it would increase ATP synthesis. Can someone explain the reasoning or the correct answer?

The answer is wrong. It would decrease ATP synthesis because remember how ATP synthesis works. A proton binds to a pocket in one of the domains of ATP synthase, which spins around. The spinning, driven by the binding and release of protons, forces the catalytic domain to release ATP, which is the RDS in the ADP + Pi ---> ATP reaction. No proton binding = no spinning = inhibition of ATP synthase.

 

[TheGoodLife570]

thank you for your replies, really helped alot!