In excitation-contraction coupling, Select one: a. calcium ions must bind with myosin to expose active sites on actin. b. myosin heads bind to exposed active sites on actin. c. cross-bridges form between myosin heads and calcium ions. d. movement of the troponin-tropomyosin complex causes actin myofilaments to slide. e. ATP binds to actin myofilaments.
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First, the action potential travels down the T-tubules and triggers the release of calcium ions from the sarcoplasmic reticulum. Show more…
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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
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When troponin binds calcium, A. it changes conformation, twisting tropomyosin and exposing actin-myosin binding sites. B. ion channels open and sodium rushes into the muscle cell. C. it allows tropomyosin to bind actin. D. it changes conformation, exposing the ATP binding site and allowing the actin-myosin bond to break. E. ATP binds to the myosin head, allowing myosin to attach to actin.
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