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Question #47651
The Question
During a prolonged marathon, an athlete's red muscle fibers predominantly utilize a specific substrate to maintain steady-state aerobic metabolism. Upon a sudden intense sprint, localized oxygen debt induces muscle fatigue. Which of the following accurately describes the metabolic transition and the corresponding Respiratory Quotient (RQ) dynamics in the muscle tissue?
Options
- A.
Metabolism shifts from fatty acid oxidation (RQ ≈ 0.7) to carbohydrate utilization (RQ ≈ 1.0), eventually leading to lactic acid fermentation where no CO₂ is evolved.
- B.
Metabolism shifts from glycogen oxidation (RQ ≈ 1.0) to beta-oxidation of fats (RQ ≈ 0.7), leading to lactic acid accumulation in the mitochondrial matrix.
- C.
The muscle shifts from aerobic respiration (RQ ≈ 0.7) to anaerobic glycolysis, resulting in an RQ greater than 1.0 due to rapid decarboxylation of pyruvate into lactic acid.
- D.
The muscle maintains fatty acid oxidation (RQ ≈ 0.7) but uncouples the TCA cycle, causing lactic acid to accumulate in the sarcoplasm with an RQ of 0.9.
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
Respiratory Quotient (RQ) Constants|Muscle Fatigue Factors|Red vs. White Muscle Fibers
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests multi-chapter synthesis (Locomotion + Respiration in Plants).
The primary trap is the misconception that all anaerobic respiration produces CO₂ (confusing lactic acid fermentation with alcoholic fermentation).
Students must also correctly link muscle histology (red fibers) to their preferred biochemical substrate (fats, RQ 0.7) and understand the sequence of metabolic shifts during oxygen debt.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | Respiratory Quotient (RQ) Constants |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |