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Question #47674
The Question
Cyanide acts as a lethal cellular poison by irreversibly binding to the Fe3+ ion of cytochrome a3 in the mitochondrial electron transport system. If actively respiring mitochondria are exposed to cyanide, which of the following statements INCORRECTLY describes the immediate biochemical fallout?
Options
- A.
Cytochrome c and the upstream electron carriers become trapped in a permanently oxidized state.
- B.
The reduction of molecular oxygen to metabolic water at Complex IV is completely arrested.
- C.
The proton motive force across the inner mitochondrial membrane collapses, halting chemiosmosis.
- D.
The NADH/NAD+ ratio in the mitochondrial matrix increases significantly due to halted oxidation.
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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
Cytochrome_a3|Complex_IV|Oxygen|ATP_Synthase
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding the redox states of electron carriers during an ETS blockade.
Students often memorize that cyanide 'stops oxidation' (oxidative phosphorylation), leading to the misconception that the carriers themselves become oxidized.
In reality, a downstream block causes all upstream components to become fully reduced because they can accept electrons but cannot offload them.
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 |