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Question #46363
The Question
A novel environmental toxin specifically inhibits Complex IV (Cytochrome c oxidase) of the Electron Transport System in human cardiomyocytes. Which of the following best describes the subsequent cascade of events leading to the disruption of the cardiac cycle?
Options
- A.
Inhibition of oxidative phosphorylation -> ATP depletion -> Failure of the Na+/K+ ATPase pump -> Inability to restore resting membrane potential -> Prolonged refractory period and arrhythmia.
- B.
Accumulation of NADH -> Activation of anaerobic glycolysis -> Lactic acid buildup -> Premature opening of voltage-gated Ca2+ channels -> Sustained cardiac tetany.
- C.
Blockade of Complex IV -> Stoppage of the mitochondrial proton pump -> Rapid efflux of K+ ions -> Hyperpolarization of the SA node -> Severe bradycardia.
- D.
Disruption of ATP synthesis -> Inability to release Ca2+ from the sarcoplasmic reticulum -> Failure of calcium-troponin binding -> Immediate diastolic arrest.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Cytochrome c|Electron Transport Chain|ATP Synthase
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The question demands cross-chapter synthesis between 'Respiration in Plants' (ETS Complex IV function) and 'Body Fluids and Circulation' / 'Neural Control' (Electrophysiology).
A common misconception is failing to link metabolic ATP production directly to the biophysical maintenance of the resting membrane potential via the Na+/K+ pump.
Additionally, Option B exploits the classic trap of 'cardiac tetany', which students often forget is impossible due to the extended plateau phase of the cardiac action potential.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Body Fluids and Circulation - Class 11 |
| Concept | Cardiac Cycle Temporal Precision |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |