Question

The further treatment of fibres with saturated salt solutions removes actin and its two associated proteins tropomyosin and troponin and also destroy the I-bands. This shows that the thin filaments are made up of................. proteins.

• A. Tropomyosin and troponin
• B. Myosin
• C. Actin
• D. None of the above

Answer 1

Answer: (C)

Actin

Muscles are composed of muscle fibres containing myofibrils, which are composed of myofilaments. There are cross-striations on the myofibrils as repeating units which are called sarcomeres which contain anisotropic and isotropic bands. The myofilaments being proteinaceous are either thick or thin filament. The thick filaments are made up of myosin molecules, while the thin filament contains three protein molecules- actin, troponin and tropomyosin. Hence when the muscle fibres are treated with saturated salt solutions, it destroys the I-bands and removes actin and its associated proteins.

Thus, the correct answer is option C.