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Excitation Contraction Coupling

During muscle...

Question

During muscle contraction, which of the following shortens?
(i) A band
(ii) I band
(iii) Sarcomere

A

i and ii

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B

ii and iii

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C

i and iii

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D

i, ii, and iii

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Solution

The correct option is B ii and iii
The A band contains thick and thin filaments overlapping with each other. The I band is formed only of thin actin filaments. The region between consecutive Z lines is a single sarcomere.

During muscle contraction, the I band is reduced in size as the overlap between the thick and thin filaments increases. The Z-lines come together, and so the sarcomere shortens as well. However, the A band does not change length during muscle contraction, since its length is the same as the length of the thick filaments.

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Similar questions

Q. During muscle contraction, which of the following shortens?
(i) A band
(ii) I band
(iii) Sarcomere

Q. Select true or false
i. Shortening of sarcomere occurs when Z lines attached to actin filaments are pushed outwards.
ii. During contraction, I bands retain their lengths.
iii. During contraction, A bands get reduced in length.

Q. During skeletal muscle contractions following events can occur:
I. I-band shortens
II. A-band shortens
III. H-zone shortens
IV. Sarcomere contract
V. ATP changes to ADP and Pi
Choose the option with incorrect events.

Q. Assess the statements.
1. A-bands of the muscle is dark and contain myosin.
2. I-bands are the light bands and contain actin.
3. During muscle contraction the A-band contracts.
4. The part between the two Z-lines is called as sarcomere.
5. The central part of thick filament, not overlapped by thin filament, called H-zone.
Of the above statements.

Q. Match the following and mark correct option:

Column I	Column II
A. Fast muscle fibres	(i) Myoglobin
B. Slow muscle fibres	(ii) Lactic acid
C. Actin filament	(iii) Contractile unit
D. Sarcomere	(iv) I-band

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Excitation Contraction Coupling

Standard XII Biology

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