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Question #45801
The Question
In certain vestigial muscles undergoing evolutionary decay due to relaxed selection, researchers observe a phenomenon where neural stimulation leads to rapid ATP hydrolysis within the sarcomere, yet absolutely no mechanical tension or muscle shortening is generated. Based on the sliding filament theory, which of the following structural protein dysregulations is the most likely cause of this futile energy consumption?
Options
- A.
A loss-of-function mutation in the ATP-binding cleft of the heavy meromyosin (HMM) head.
- B.
A mutation in the actin-binding domain of the myosin head that prevents stable cross-bridge formation despite normal ATP cleavage.
- C.
A mutation in the TpC subunit of troponin that permanently prevents the binding of Ca2+ released from the sarcoplasmic reticulum.
- D.
A mutation causing the continuous active transport of Ca2+ back into the sarcoplasmic cisternae, preventing F-actin unmasking.
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
Actin_Filaments|Tropomyosin|Evolutionary_Atrophy
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that any loss-of-function mutation in a vestigial muscle simply shuts down the entire machinery.
The pivot here is distinguishing between the ATPase activity (energy consumption) and the actin-binding capability (mechanical tension) of the Heavy Meromyosin (HMM) head.
Common Misconception: Failing to realize that if calcium cannot bind troponin (Option C) or is pumped away (Option D), the cross-bridge cycle doesn't just fail to produce tension; it fails to consume ATP continuously, because the myosin head cannot release ADP and Pi without completing the power stroke.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Cross-bridge Cycling Energy |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |