Question

Read the following statements:

(a) Each thin filament is made of two F-actins.

(b) Each G-actin is polymer of F-actins.

(c) Two filaments of tropomyosin run close to the F-actins throughout it's length.

(d) Troponin is distributed at irregular internals on the tropomyosin.

(e) During contracted state a subunit of troponin masks the actin binding sites for myosin on the actin filaments.

Choose the correct statement(s).

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

Answer 1

The correct option is A a and c

Each actin (thin) filament is made of two ‘F’ (filamentous) actins. Each ‘F’ actin is a polymer of monomeric ‘G’ (globular) actins. Two filaments of another protein, tropomyosin, also run close to the ‘F’ actins throughout its length. A complex protein troponin is distributed at regular intervals on the tropomyosin. In the resting state, a subunit of troponin masks the active binding site for myosin on the actin filaments.