Multiple Choice
In skeletal muscle contraction, the thin filaments of the sarcomere are primarily composed of which protein?
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8. Protein Function
Skeletal Muscle Contraction
Multiple Choice
In skeletal muscle contraction, a skeletal muscle fiber deprived of adequate ATP supplies will most likely:
A
Remain in a sustained contracted (rigor) state because myosin heads cannot detach from actin
B
Show increased calcium reuptake into the sarcoplasmic reticulum because SERCA activity is enhanced without ATP
C
Continue normal contractions because ATP is required only for troponin binding to calcium
D
Relax completely because cross-bridge cycling requires ATP only for myosin binding to actin
Verified step by step guidance1
Understand the role of ATP in skeletal muscle contraction, particularly in the cross-bridge cycle between actin and myosin filaments.
Recall that ATP is necessary for the detachment of myosin heads from actin after a power stroke; without ATP, myosin remains bound to actin, causing a sustained contraction known as rigor.
Recognize that calcium reuptake into the sarcoplasmic reticulum by the SERCA pump requires ATP, so ATP deprivation would reduce, not enhance, calcium reuptake.
Note that ATP is not required for troponin binding to calcium; rather, ATP is essential for the mechanical steps of contraction and relaxation.
Conclude that without ATP, muscle fibers cannot relax properly because myosin heads cannot detach from actin, leading to a rigor state rather than normal relaxation or contraction.
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