Multiple Choice
In skeletal muscle sarcomeres, which protein is the primary component of the thick filaments?
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8. Protein Function
Skeletal Muscle Contraction
Multiple Choice
In skeletal muscle cross-bridge cycling, what is the primary role of ATP binding and hydrolysis on the myosin head?
A
ATP binding directly causes the power stroke by pulling actin past myosin.
B
ATP binding detaches myosin from actin, and ATP hydrolysis cocks (energizes) the myosin head for the next power stroke.
C
ATP hydrolysis increases cytosolic by opening ryanodine receptors on the sarcoplasmic reticulum.
D
ATP binding exposes myosin-binding sites on actin by moving tropomyosin away from the binding groove.
Verified step by step guidance1
Understand the role of ATP in the cross-bridge cycle of skeletal muscle contraction, focusing on the interaction between myosin heads and actin filaments.
Recognize that ATP binding to the myosin head causes the myosin to detach from the actin filament, which is essential for breaking the existing cross-bridge.
Know that after detachment, ATP is hydrolyzed by the myosin head into ADP and inorganic phosphate (Pi), which provides the energy to 'cock' or energize the myosin head into a high-energy conformation.
This energized myosin head can then bind to a new position on the actin filament, ready to perform the power stroke when ADP and Pi are released.
Note that ATP binding and hydrolysis do not directly cause the power stroke or increase cytosolic calcium; instead, they regulate the detachment and re-energizing steps necessary for continuous muscle contraction.
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