객관식
Which of the following correctly lists the steps of muscle fiber contraction in the proper sequence?
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9. Muscle Tissue
Steps of Muscle Contraction
객관식
In the steps of skeletal muscle contraction, what is the primary role of released from the sarcoplasmic reticulum?
A
It binds to troponin, causing tropomyosin to move and expose myosin-binding sites on actin
B
It binds directly to myosin heads to provide the energy for the power stroke
C
It prevents ATP from binding to myosin, maintaining the rigor state
D
It activates acetylcholinesterase to terminate the signal at the neuromuscular junction
검증된 단계별 안내1
Understand that during skeletal muscle contraction, calcium ions (Ca^{2+}) are released from the sarcoplasmic reticulum into the cytoplasm of the muscle fiber.
Recognize that the primary role of Ca^{2+} is to bind to the regulatory protein troponin, which is located on the thin filament (actin).
When Ca^{2+} binds to troponin, it induces a conformational change that causes tropomyosin, another regulatory protein, to shift its position on the actin filament.
This movement of tropomyosin exposes the myosin-binding sites on actin, allowing the myosin heads to attach and initiate the cross-bridge cycle necessary for muscle contraction.
Note that Ca^{2+} does not bind directly to myosin heads, prevent ATP binding, or activate acetylcholinesterase; its key function is to regulate the exposure of binding sites on actin through troponin.
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