Question

Read the following A to D statements and select the one option that contains both correct statements.

a. Z-line is present in the centre of the light band
b. Thin filaments are firmly attached to the M-line
c. The central part of thick filaments, not overlapped by thin filaments is called Z-band
d. Light band contains only thin filaments

• A. a and d
• B. b and c
• C. a and c
• D. b and d

Answer 1

The correct option is A a and d

Myofibrils are formed by the arrangement of a large number of parallel filaments. Dark and light bands are the main characteristic features of a myofibril. The dark bands are referred to as A-bands, whereas the light bands are called I-bands. Light band contains only thin filaments.

Thick filaments are attached to M-line.
A-zone that is comparatively less dark, is present at the centre of the A-band and is called the H-zone. It is the central part of thick filament, which is not overlapped by thin filaments. The H-zone has the M-line in the middle of it.

Z-band which is a dark membrane, is present at the centre of each I-band. The sarcomere is the part of the myofibril which is present between two successive Z-lines.


Hence, the correct statements are 'a and d'.