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Question #45916
The Question
Cyanide acts as a deadly metabolic poison by binding to the Fe3+ ion of cytochrome a3 in the mitochondrial electron transport chain. Which of the following represents the most accurate immediate consequence of this inhibition in an actively respiring cell?
Options
- A.
Oxygen continues to act as the terminal electron acceptor, but the pumping of protons by Complex IV is specifically halted.
- B.
Cytochrome c remains in a permanently oxidized state, leading to the rapid dissipation of the proton motive force.
- C.
The transfer of electrons from cytochrome c to oxygen is blocked, causing all preceding ETC carriers to accumulate in their reduced forms.
- D.
The F0-F1 ATP synthase is directly inhibited, forcing the cell to shift entirely to anaerobic glycolysis to maintain ATP levels.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Terminal Electron Acceptor|Cytochrome c Oxidase|Oxygen
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding the redox states of electron carriers during an ETC blockage.
A common misconception is failing to distinguish between direct inhibition of ATP synthase and the indirect cessation of ATP synthesis due to a collapsed proton gradient.
Furthermore, students often struggle to deduce that blocking the end of a pathway causes upstream intermediates to accumulate in their reduced (electron-rich) state rather than their oxidized state.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | Terminal Electron Acceptor |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |