During the contraction of a vertebrate skeletal muscle fiber, calcium ions a. break cross-bridges by acting as a cofactor in the hydrolysis of ATP. b. spread action potentials through the T tubules. c. re-establish the polarization of the plasma membrane following an action potential. d. transmit action potentials from the motor neuron to the muscle fiber. e. bind with troponin, changing its shape so that the myosin-binding sites on actin are exposed.
Added by Bryan S.
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Step 1: Calcium ions bind with troponin in the muscle fiber. Show more…
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During vertebrate skeletal muscle contraction, calcium ions (A) break cross-bridges as a cofactor in hydrolysis of ATP. (B) bind to troponin, exposing myosin-binding sites. (C) transmit action potentials to the muscle fiber. (D) spread action potentials through the T tubules.
Madhur L.
Calcium plays what role in skeletal muscle contraction? a. Binds the myosin head, opening up cross-bridge formation sites on actin b. Binds tropomyosin, causing a conformational change that moves troponin, unblocking the crossbridge formation site on the actin c. Binds globular actin, rolling the tropomyosin from its position, and unblocking the cross-bridge binding site on troponin d. Binds troponin, causing a conformational change that moves tropomyosin, opening up the cross-bridge formation site on the actin molecules
Sri K.
During contraction of skeletal muscle: a. ATP stimulates $\mathrm{Ca}^{2+}$ to move out of the cytosol, which allows tropomyosin to bind myosin causing contraction of the thin filament. b. myosin crossbridges use ATP to relax the molecular spring in the myosin head, which pulls the thick filaments away from the thin actin filaments. c. actin binds ATP, allowing troponin in the thick filaments to form the myosin crossbridge. d. action potentials cause the release of $\mathrm{Ca}^{2+}$ allowing tropomyosin fibers to uncover the actin binding sites needed for the myosin crossbridge. e. botulinum toxin could increase the release of acetylcholine at the contracting muscle site.
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