4 The ATP solution that you used in your muscle contraction procedure contains m

Question

4 The ATP solution that you used in your muscle contraction procedure contains maghesium lons, Which increase the strength of contraction in glycerinated muscle. In living muscle cells, magnesium ions compete with calcium ions for binding sites on troponin molecules. In the condition of hypermagnesemia-a high concentration of magnesium ions in the blood-magnesium ions can prevent calcium ions from binding troponin. Would this strengthen, weaken, or have no effect on the muscle contraction? Explain.

Explanation / Answer

Calcium is released from the terminal cisternae of sarcoplasmic reticulum upon stimulation by an action potential. Calcium binds to troponin, thereby allowing tropomyosin to move away from troponin. This action will expose binding sites on actin. As a result, myosin binds to actin. There is ATP hydrolysis causing cross bridging. Hence, muscle contraction will occur.

Excess Magnesium ions prevent the binding of calcium to troponin. As a result, troponin is still bound to tropomyosin, preventing cross bridging. Hence, muscles will relax. Reduced muscle contraction will make the muscles weak. Hypermagnesemia will weaken muscke contraction.

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