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Locomotion and Movement question

2021 · Q80
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Locomotion and Movement question

2021 · Q80

NEETBiologyLocomotion and MovementMCQ+4 / −1
During muscular contraction which of the following events occur?

(1) 'H' zone disappears

(2) 'A' band widens

(3) 'I' band reduces in width

(4) Myosine hydrolyzes ATP, releasing the ADP and Pi.

(5) Z-lines attached to actins are pulled inwards.

Choose the correct answer from the options given below.
  1. A
    (2), (4), (5), (1) only
  2. B
    (1), (3), (4), (5) only
  3. C
    (1), (2), (3), (4) only
  4. D
    (2), (3), (4), (5) only
View written solutionFree

Correct answer: B

The correct option is (b) because the length of A-band is retained. During muscle contraction, the following events occur:

(1) The globular head of myosin acts as ATPase and hydrolysis ATP molecule and eventually leads to the formation of cross bridge.

(2) This pulls the actin filament towards the centre of 'A-band'.

(3) The Z-line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere.

(4) The thin myofilaments move past the thick myofilaments due to which the H-zone narrows. This reduces the length of I-band but retains the length of A-band.

(5) The myosin then releases ADP + Pi, and goes back to its relaxed state.

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