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Question #45781
The Question
A researcher is studying a rare genetic disorder in Homo sapiens characterized by a missense mutation that completely abolishes the ATPase activity of the calcium pumps located on the sarcoplasmic reticulum (SR) membrane of skeletal muscles. If a muscle fiber from this patient receives a single, threshold neural stimulus, which of the following physiological consequences will be observed?
Options
- A.
The muscle fiber will fail to contract entirely because the masking of myosin-binding sites on actin cannot be removed.
- B.
The muscle fiber will contract but fail to relax, resulting in a sustained state of contraction as the 'Z' lines cannot return to their original position.
- C.
The cross-bridge cycle will terminate prematurely due to the inability of the myosin head to hydrolyze ATP for the power stroke.
- D.
The action potential will fail to spread through the T-tubules, preventing the initial release of calcium ions into the sarcoplasm.
Check Your Answer
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
Troponin|Tropomyosin|IP3_Pathway|Sarcoplasmic_Reticulum
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Differentiating between the passive release of calcium (which initiates contraction) and the active sequestration/pumping back of calcium (which initiates relaxation).
Common Misconception: Students often assume that any failure in a 'calcium pump' means the muscle cannot contract, confusing the active transport pumps (SERCA) responsible for relaxation with the voltage-gated release channels responsible for contraction.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Myofilament Protein Composition |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |