stucture of myofibril

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Please find below the solution to the asked query
  • Myofibrils or myofilaments  (parallel arrangement of filaments) are present inside the sarcoplasm of muscle fibre.

  • Structure of  Myofibril:

    • Each myofibril has alternate light and dark bands on it (striated appearance).

    • Light band: Contains the protein actin and is called the I band (Isotropic band)

    • Dark band: Contains the protein myosin and is called the A band (anisotropic band)

    • Actin: Thin filament; Myosin: Thick filament

    • Actin and myosin are arranged parallel to each other as rod-like structures.

    • Z line:  An elastic fibre which bisects the I band. Portion between two Z lines represents a functional sarcomere.

    • In resting state, the thick filament partially overlaps the free ends of the thin filament.

    • H  zone: The zone where the thick filaments are not overlapped by the free ends of the thin filament

    • M line:  Holds the dark band at the centre; thus, it bisects the H zone.  


Hope this information will clear your doubts about the structure of myofibril.
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1)The filaments of myofibrils, myofilaments, consist of two types, thick and thin:

2)Thin filaments consist primarily of the protein actin,
Thick filaments consist primarily of the protein myosin, held in place by titin filaments. Myosin is responsible for force generation. It is composed of a globular head with both ATP and actin binding sites, and a long tail involved in its polymerization into myosin filaments. 
the following image will help u to understand them more clearly :-

hope it helps u :)
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