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Read the following statements

                        I.    The thin filament is made up of the globular protein called myosin

                      II.    The thick filament is made up of the protein called actin

                     III.    In the centre of each 'I' band is an elastic fibre called 'H' line                                  which bisects it.

                     IV.    The central part of the thick filament is not overlapped by thin                                 filaments and is called the 'H' zone.

 

Choose the option representing all correct statements.

 

Option: 1

I\; and\; II


Option: 2

II,III\: and\: IV


Option: 3

III only


Option: 4

IV only


Answers (1)

best_answer

 

 

Sarcomere -

  • The smallest unit of the skeletal muscle is called the sarcomere.
  • The sarcomere consists of the thick and thin filament. 
  • The thin filament is made up of the globular protein called actin.
  • The thick filament is made up of the protein called myosin.
  • The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called ‘A’ 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. 
  • In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it.
  • The thin filaments are firmly attached to the ‘Z’ line.
  • The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called ‘M’ line. 
  • The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils. 
  • The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere. The length of a sarcomere is about 2 -3 micron
  • In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filaments.
  • This central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.

Hence,the correct option is d. Only IV

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Posted by

Kuldeep Maurya

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