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Question #45909
The Question
In the electron transport systems of both chloroplasts and mitochondria, mobile lipid-soluble carriers play a crucial role in proton translocation via a Q-cycle. Which of the following statements accurately describes the functional homology and electron transfer sequence of these carriers?
Options
- A.
Plastoquinone is reduced by PSII and oxidized by the Cytochrome b6f complex, analogous to Ubiquinone being reduced by Complex I or II and oxidized by Complex III.
- B.
Both carriers facilitate the active pumping of protons from the thylakoid lumen or mitochondrial intermembrane space into the stroma or mitochondrial matrix.
- C.
Plastoquinone transfers electrons directly to Photosystem I, whereas Ubiquinone transfers electrons directly to Cytochrome c oxidase (Complex IV).
- D.
Ubiquinone is a proteinaceous carrier located on the outer surface of the inner mitochondrial membrane, functionally similar to Plastoquinone on the thylakoid membrane.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Complex_III|Cytochrome_bc1|Photosystem_II|PQ
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the photosynthetic and mitochondrial ETS sequences independently without recognizing the evolutionary and functional homology between the Cyt b6f complex and Complex III (Cyt bc1), and their respective mobile carriers (PQ and UQ).
The trap relies on confusing the exact sequence of electron acceptors, the direction of proton pumping (matrix/stroma to IMS/lumen), and the biochemical nature of the carriers (lipid-soluble vs. proteinaceous).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | ETS Complex Specificity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |