Question

In actomyosin complex, for one unit of actin the number of units of myosin is
a. 1
b. Variable
c. 3
d. 4

Answer 1

Hint: We all know that a muscle fiber contains parallel arranged myofibrils in sarcoplasm and these myofibrils have actin protein and myosin protein. The actomyosin is a contractile protein formed by the combination of actin and myosin with the help of ATP during the muscle contraction process.

Complete answer:
Actin protein is a thin filament and myosin protein is the thick filament. Both of these proteins are the force-generating contractile and polymerized proteins and are arranged parallel to each other. Both are involved in the mechanism of muscle contraction.
• The muscle contraction starts when a neural signal reaches the neuromuscular junction from CNS through the motor neuron.
• Release of calcium ions occurs which binds with troponin and causes the active site of actin to open for myosin. The myosin head then binds with the open active sites of actin and forms a cross-bridge called actomyosin. This cross-bridge is formed when one unit of myosin binds in the active site of one unit of action with the help of ATP.
• When the thin actin slides over the thick myosin then it causes the contraction of muscles. This process is continued until the calcium ions are returned back to the sarcoplasmic reticulum.

Hence, the correct answer is option (A).

Note: Each actin filament has two filamentous actions helically wound to each other and they are polymers of monomeric globular actions. Each myosin has two parts: a globular head which contains an ATPase enzyme having the binding sites for ATP and active sites for actin, and a tail.