You artificially raise the calcium concentration inside the myofibrils and obser

Question

You artificially raise the calcium concentration inside the myofibrils and observe that both the normal and dysgenic fibers contract. From this observation, where would you conclude that the defect occurs in the steps of muscle contraction? Briefly explain how you came to this conclusion. a. Exposure of the active sites on actin b. Binding of the calcium to troponin c. Release of the calcium ions from the sarcoplasmic reticulum into the myofibril d. The repeated cycles of cross-bridge formation, myosin power strokes, and detachment

Explanation / Answer

Calcium ions are an intracellular signaling molecule for muscle contraction .Calcium binds to troponin-C to initiate contraction and this will continue until excitation ceases.In a relaxed muscle, tropomyosin blocks the attachment site for the myosin crossbridge, thus preventing contraction. Some of this calcium attaches to troponin, which causes it to change shape, exposing binding sites for myosin (active sites) on the actin filaments.

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