Question

Which of the following statements regarding the structure of contractile proteins are correct ?
I. Each actin filaments is made up of two ' F ' actins, which are wound helically around each other.
II. Two types of troponins are distributed at regular intervals on the tropomyosin .
III. The globular head of meromyosin has binding sites for ATP and troponins.
IV myosin is a structure proteins which also has enzymatic activity.

Answer 1

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Read the statements regarding muscle proteins and identify the correct statements

i. Actin is a thin filament and is made up of two F-actins

ii. Complex protein, tropomyosin is distributed at regular intervals on the troponin

iii. Myosin is a thick filament which is also a polymerized protein

iv. Globular head of meromyosin consists of light meromyosin (LMN)

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Solution

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Correct option is

C

i, ii and iii are correct

Myofibril is made up of two types of filaments.They are thin filament(actin) and thick filament(myosin).

Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. 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.

Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins, constitute one thick filament. Globular head of meromyosin consists of Heavy meromyosin (HMM).

So, the correct answer is 'i, ii and iii are correct'