Question

Discuss the role of Ca2+ ions in muscle contraction. Draw neat sketches to illustrate your answer.

Answer 1

Role of Ca²⁺ ions in muscle contraction

1. Calcium plays a key regulatory role in muscle contraction.
2. These ions bind to troponin causing a change in its shape and position.
3. This in turn alters the shape and position of tropomyosin.
4. This shift exposes the active sites on the F-actin molecules and myosin cross-bridges able to bind to these active sites.
5. The complete process is outlined in the figure below.
6. The head of each myosin molecule contains an enzyme myosin ATPase.
7. In the presence of myosin ATPase, Ca²⁺ , and Mg²⁺ ions, ATP breaks down into ADP and inorganic phosphate as ATP
8. Myosin ATPase−−−−−−−−−→Ca²⁺,Mg²+ADP+Pi+Energy
9. Energy from ATP causes energized myosin cross-bridges to bind with actin.