Locomotion and Movement Test - 37

 In the given figure depicting an actin filament, the unidentified parts are:

A: Troponin (Troponin is a calcium-regulatory protein that is distributed regularly along the entire length of thin filaments and forms an ordered complex with tropomyosin and actin).

B: Tropomyosin (A protein found in the actin filaments in muscles).

C: F-actin (Fibrous actin polymerized in the form of a double-helix produced in the presence of a metal cation and ATP). 

So, the correct answer is 'A - Troponin B - Tropomyosin C - F-actin'.

• The thin filaments contain three different proteins— F-actin, tropomyosin, and troponin. 
  
• The two actin proteins are filamentous proteins that are helically arranged together with protein tropomyosin that lies in the grooves of the helix as well as an associated globular protein troponin, found at intervals along the filament for masking binding site for myosin. 
  

• Amoeboid movement is like the crawling type of movement accomplished by protrusion of cytoplasm of a cell involving the formation of pseudopodia. For example leucocytes.
• Ciliary movement is the rhythmic, sweeping movement of the epithelial cell cilia possibly resulting from the alternate contraction and relaxation of contractile thread. For example Trachea.
• Flagellar movement consists of contraction waves that pass either from the base to the tip of the flagellum or in the reverse direction to produce forward or backward movement. For example Spermatozoa.
• Muscular movement is the movement where muscles are attached to the bones or internal organs or blood vessels. For example Limbs.

• Tropomyosin is a protein found in the actin filaments in muscles. 
• The molecule contains two elongated strands that run along the length of the filament. When the muscle is at rest, the tropomyosin molecule covers the binding site of the actin molecule, where interaction with myosin occurs.
• On contraction of the muscle, the tropomyosin is displaced by another protein, troponin, allowing the interaction of actin with myosin.