STD 11 - 4. Animal kingdom — NEET STD 11 Science — Question

Myofibrils are structural constituent of muscle fibre, select correct statement for myofibril :
(i) Each myofibril has alternate dark and light bands on it.
(ii) Striated appearance of myofibril is due to the distribution pattern of two important proteins- actin and myosin.
(iii) The light bands contain myosin and is called I- band or isotropic band, whereas the dark band called A or Anisotropic band contains actin.
(iv) Actin filaments are thicker as compared to the myosin filaments, hence are commonly called thick and thin filaments respectively.
(v) In the centre of each A-band is an elastic fibre called Z-line which bisects it.
(vi) The thick filaments in the A-band are held together in the middle of this band by a thin fibrous membrane called M-line.
(vii) The portion of the myofibril between two successive Z-lines is considered as the functional unit of contraction and is called a sarcomere.

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