Discuss the role of `Ca^(2+)` ions in muscle contractions. Draw neat sketches to illustrate your answer.

Explanation

Calcium plays a key regulatory role in muscle contraction. These ions bind to troponin causing change in its shape and position. This in turn alters the shape and position of tropomyosin. This shift exposes the active sites on the F-actin molecules and myosin cross-bridges able to bind to these active sites.
The complete process is outlined in the figure below

Role of calcium ion, is the contraction and relaxation process. The head of each myosin molecule contains an enzyme myosin ATPase. In the presence of myoosin ATPase, `Ca^(2+) and Mg^(2+)` ions, ATP breaks down into ADP and inorganic phosphate as
`ATPunderset(Ca^(2+),Mg^(2+))overset("Myosin ATPase")rightarrowADP+P_(i)+"Energy"`
Energy from ATP causes energised myosin cross-bridges to bind with actin.