Which of the following is not involved in muscular contraction?

• Calcium ion

• Troponin

• Actin

• Magnesium ion

D.

Magnesium ion

Muscle contraction is the shortening or tensing of a part or organ (i.e., a muscle fibre). Magnesium ion is not involved directly in the process of muscle contraction.

Actin and troponin are the globular proteins made up of two and three globular peptides respectively. Calcium ion also play a key regulatory role in muscle contraction, i.e., increase in the calcium ion levels lead to their binding to the troponin subunit.