Multiple Choice
In the steps of skeletal muscle contraction, what is the primary role of released from the sarcoplasmic reticulum?
13
views
9. Muscle Tissue
Steps of Muscle Contraction
Multiple Choice
During skeletal muscle contraction, what is the primary role of calcium ions () in enabling cross-bridge cycling?
A
It binds directly to myosin heads to power the power stroke by releasing inorganic phosphate
B
It binds to troponin, causing tropomyosin to shift and expose myosin-binding sites on actin
C
It is hydrolyzed by myosin ATPase to provide energy for the sliding filament mechanism
D
It is pumped into the sarcoplasmic reticulum to initiate depolarization of the sarcolemma
Verified step by step guidance1
Understand the structure of the thin filament in skeletal muscle, which includes actin, tropomyosin, and troponin. Tropomyosin blocks the myosin-binding sites on actin when the muscle is relaxed.
Recognize that calcium ions (Ca^{2+}) are released from the sarcoplasmic reticulum into the cytoplasm when a muscle fiber is stimulated to contract.
Know that Ca^{2+} binds specifically to the troponin complex on the thin filament. This binding causes a conformational change in troponin.
This conformational change in troponin causes tropomyosin to shift its position, exposing the myosin-binding sites on actin filaments.
With the myosin-binding sites exposed, myosin heads can attach to actin, forming cross-bridges, which is essential for the cross-bridge cycling and muscle contraction to proceed.
Related Videos
Related Practice
