Correct option is C
Explanation-
Option C -"The ATP synthesis reaction is driven by coupling to an electrochemical potential across the inner mitochondrial membrane."
In the mitochondria, ATP synthase works as a proton-driven rotary motor. The Fo portion (embedded in the inner mitochondrial membrane) allows protons to flow through, creating a proton motive force (electrochemical gradient). This force drives conformational changes in the F₁ subunit, enabling it to synthesize ATP from ADP and Pi.
However, when F₁ is isolated (soluble form), it is no longer coupled to this gradient, and instead hydrolyzes ATP. The key difference is the presence or absence of the proton gradient, not just structural differences.
Incorrect options-
Option A- "A conformational change in the F₁ subunit between the two environments"
While conformational changes are involved in ATP synthesis, they are driven by proton flow through Fo. Saying it's just a conformational change without referencing the proton motive force doesn't fully explain the mechanism. So it's incomplete and not the best explanation.
Option B - "The lipid bilayer environment facilitates the synthesis of ATP by enhancing the rate of the dehydration reaction"
The lipid bilayer itself does not directly enhance dehydration or ATP formation. The lipid bilayer’s role is to maintain the proton gradient, but it is the gradient, not the lipid, that directly drives synthesis. So this is misleading.
Option D - "In the soluble form, the electrochemical potential drives the F₁ subunit to hydrolyze ATP"
This is incorrect because the soluble F₁ is not exposed to the electrochemical gradient. That gradient exists only across membranes. So, in the soluble form, F₁ hydrolyzes ATP because it lacks the gradient, not because it's being driven by it.
So, the correct answer is option C - The ATP synthesis reaction is driven by coupling to an electrochemical potential across the inner mitochondrial membrane
