Which of these events is necessary for the contraction of a muscle cell? A. the shortening of myofi laments. B. the conversion of ADP & HPO 4 2− to ATP in the cross-bridge. C. Ca 2+ binding to troponin causing it to change shape. D. the movement of ACh from the sarcolemma to the axon terminal.
Option C. The binding of calcium is necessary. calcium ions bind to the protein comple troponin in order to put off the covering of active site on actin
