What type of filaments do sarcomeres contain?

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Feb 11, 2018


  • Actin filament or thin filament
  • Myosin filament or thick filament.


Ultrastructure of sarcomere contains two types of myofilaments i.e actin(thin) & myosin(thick) filaments.

  • Thin Filament :
    Thin filament is #7-8nm"# in diameter. Thin filament extends the entire length of #"I-band"#. It is composed of three proteins that are:

#(a)# Actin #to# The thin filaments are composed chiefly of actin proteins. That's why these filaments are also called as actin filaments. The actin molecules are arranged in to chains. This chains twist around each other like twisted double strand of pearls.

#(b)# Tropomyosin #to# Two strands of another protein twist around actin, This protein is tropomyosin.

#(c)# Troponin #to# This is another major protein in thin filament. It is actually #3# polypeptide complex out of which one binds to actin, another binds to tropomyosin. And the third one bind calcium ions#(Ca^(2+))# in order to start muscle contraction.

  • Thick Filament:
    Thick filament is located at the centre of the sarcomere. It is about #16nm# in diameter and it's mainly composed of myosin protein. The thick filament extends the entire length of #"A-band"#.

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