Question

Contractile proteins are found in
A. Bones
B. Blood
C. Muscles
D. Cartilage

Answer 1

Connective tissues are most abundant and widely distributed in the body of complex animals. They are named connective tissue because of their special functional linking and supporting other tissues or organs of the body.

Complete answer :
Muscle is a specialized tissue of mesodermal origin. they have special properties like excitability, contractility, ( due to the presence of contractile protein ) extensibility, and elasticity. Contractile proteins are of two types actin and myosin. Each actin filament is known as a thin filament. The actin filament is made up of two filamentous actin as a helical wound to each other. Each F actin is a polymer of monomeric G or globular actin. Tropomyosin also runs close to the F actin throughout its length. Troponin is distributed at regular intervals on the tropomyosin.
The second contractile protein is myosin filament also known as thick filament. Myosin is also a polymerized protein. Many monomeric proteins called meromyosin constitute one thick filament. Each meromyosin has two important parts: heavy meromyosin and light meromyosin.
So, the correct answer is (C).

Additional information:
-The light band contains actin and it’s called I-band or isotropic band.
-The dark band called the A-band or anisotropic band contains myosin.
-Both the proteins are arranged as rod-like structures parallel to each other and also to the longitudinal axis of the myofibrils .

Note: The A band and I band are arranged alternately throughout the length of the myofibrils . The portion of the myofibrils between two successive Z lines is considered as the functional unit of contraction and it is called a sarcomere.