A muscle fiber contracts by a sequence of events initiated by the binding of acetylcholine to its receptor.Which of the following is the correct sequence? I-The calcium-troponin complex pulls tropomyosin away from the myosin binding sites of actin.
II-The freed-sites of actin bind to myosin to form cross bridges.
III-Calcium ion binds to the troponin.
A)I,III,and II
B)III,II,and I
C)II,III,and I
D)I,II,and III
E)III,I,and II

Question

Quizplus · Accepted Answer

The correct sequence starts with calcium ion binding to troponin (III), which then leads to the calcium-troponin complex pulling tropomyosin away from the myosin binding sites on actin (I), allowing the freed sites of actin to bind to myosin and form cross bridges (II).

A Muscle Fiber Contracts by a Sequence of Events Initiated