Movement of H+ in mitochondria

[4s4]

I'm kind of confused about the whole electron transport chain business and chemiosmotic theory. Is the movement of H+ from the intermembrane space to matrix DOWN the gradient or against? This came up on Kaplan 6 BS and I'm not really getting their explaination. Thanks!

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[BigRedPremed]

It should be down the gradient.

 

[4s4]

If it's down...then ATP synthesis occurs according to the passage by the "re-entry of protons into the matrix" so when H+ goes down the gradient, then ATP is made...so why does the question (#152) say that "Nigericin is an agent that carries H+ down its concentration gradient" and the answer is that bacteria will be less efficient in making ATP? Shouldn't they be MORE efficient at making ATP?

 

[BigRedPremed]

Um, I took the MCAT a year ago and don't know the exact passage you are referencing. My guess is that it would destroy the H+ gradient that is needed to generate ATP. Remember, that ATP is only generated when H+ flows down its gradient THROUGH ATP synthase. If there is a drug that moves H+ down the gradient w/o having to pass through the synthase, you get a reduced gradient w/o generating any ATP. Just my guess.

 

[Sol Rosenberg]

Good guess. That is the reason.

 

[4s4]

Ohhh, makes sense. Thanks!

 

[Foolins]

Because in the mitochondria, the only route for H+ down its gradient should be the channels coupled to ATP synthase.

If you had some another way of transporting H+ down its gradient without going through the ATP synthase...then it would go back into the matrix for nothing.