The figure above shows an organelle typically found in eukaryotic cells. Which of the following best describes the function of the double membrane system of this organelle?

Question

BlackTom AI · Accepted Answer

The inner mitochondrial membrane contains the electron transport chain complexes and ATP synthase that pump and harness protons to make ATP, so the correct choice is that the inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix.

1) Relevant knowledge points and concepts
- The organelle shown is a mitochondrion with an outer membrane, an inner membrane (with cristae), an intermembrane space, and a matrix.
- Oxidative phosphorylation occurs at the inner membrane: electron transport chain (ETC) protein complexes transfer electrons from NADH/FADH2 and actively pump H+ from the matrix into the intermembrane space.
- The resulting proton (H+) electrochemical gradient (proton motive force) drives ATP synthase to convert ADP + Pi into ATP when H+ flows back into the matrix.
- The outer membrane contains porins and is relatively permeable to small molecules; the inner membrane is highly impermeable and selectively controls ion/protein transport.

2) Step-by-step reasoning
- NADH/FADH2 deliver electrons to ETC complexes embedded in the inner membrane.
- Electron flow powers conformational changes in complexes I, III, and IV that translocate protons from matrix → intermembrane space.
- This builds a high H+ concentration in the intermembrane space relative to the matrix.
- ATP synthase (also in the inner membrane) allows protons to return to the matrix and uses that flow to synthesize ATP.

3) Calculations
- Not applicable (no numeric computation required).

4) Why the correct answer is correct
- It precisely describes the fundamental role of inner-membrane proteins in creating a proton gradient across the inner membrane, which is the basis for mitochondrial ATP production.

5) Why the other options are incorrect
- Options invoking sodium ion gradients are wrong: mitochondria use H+ gradients, not Na+, for ATP synthesis.
- Statements that the inner membrane establishes gradients used for glucose are incorrect: glucose synthesis is not performed by the inner membrane; mitochondria produce ATP.
- Claiming the outer membrane allows transport of all molecules is false: it is permeable to small solutes via porins but not to large proteins, and the inner membrane is the main regulatory barrier.

6) Conclusion
- The correct answer is: "The inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix." This matches the provided answer.

The figure above shows an organelle typically found in eukaryotic cells. Which of the following best describes the function of the double membrane system of this organelle?单项选择题

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