Question

How many protons are released on the cytoplasmic side of Inner Mitochondrial Membrane by complex III for every two protons taken up from its matrix side?

• A. Four
• B. Two
• C. Eight
• D. One

Hint:

Complex III Q cycle:
- 2 H+ taken up from matrix side.
- 4 H+ released on cytoplasmic side.
- Contributes to the proton-motive force.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question tests knowledge of the electron transport chain and the Q cycle in Complex III.

Step 2: Detailed Explanation:
Complex III (cytochrome bc1) operates via the Q cycle.
For every two protons taken up from the matrix side:
- Four protons are released on the cytoplasmic side.
- Two electrons are transferred.
This is the stoichiometry of the Q cycle.
Thus, for every two protons taken up, four protons are released.

Step 3: Final Answer:
Thus, four protons are released, which corresponds to option (A).
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