What is the role of Ca2+ in the control of muscle contraction? a. It causes depolarization of the T-tubule system. b. It binds to tropomyosin and breaks actin-myosin cross-bridges. c. It changes the conformation of troponin, which ultimately results in myosin-binding sites being exposed. d. It changes the conformation of myosin heads, causing actin and myosin filaments to slide past each other. e. It blocks the ATP-binding site on myosin heads, enabling muscles to relax.
Added by Timothy G.
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This Ca2+ binds to the protein complex troponin, which is located on the thin filaments of muscle cells. This binding causes a conformational change in troponin, which ultimately results in the exposure of myosin-binding sites on the actin filaments. Once the Show more…
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The role of $\mathrm{Ca}^{2+}$ in the control of muscle contraction is to a. cause depolarization of the T tubule system. b. change the conformation of troponin, thus exposing myosin-binding sites. c. change the conformation of myosin heads, thus causing microfilaments to slide past each other. d. bind to tropomyosin and break actinmyosin cross-bridges. e. block the ATP-binding site on myosin heads, enabling muscles to relax.
The function of Ca2+ in skeletal muscle contraction is to a. cause an allosteric change in myosin so that it detaches from actin. b. provide the energy necessary for the movement of the cross-bridge. c. expose the myosin-binding sites on the thin filaments. d. stimulate an action potential in the muscle fiber. e. do a and c only.
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