Question

Which of the following statements about the molecular arrangement of actin and myosin in myofibrils is incorrect?

i	Each actin (thin filament) is made of 2F(filamentous) actins.
ii	F-actin is the polymer of G(globular) actin
iii	2F actins are twisted into a helix.
iv	Two strands of tropomyosin (protein) lie in the grooves of F-actin.
v	Troponin molecules (Complex) protein are distributed at regular intervals on the tropomyosin
vi	Troponin forms the head of the myosin molecule
vii	The myosin is a polymerized protein

Answer 1

Hint:
Proteins constitutes the muscles. In muscles, myosin and actin are present which are protein molecules. The chief function of these is the involvement of the contraction of muscles.

Complete step by step answer:
Voluntary muscular movement of the body is controlled by actin and myosin along with troponin, tropomyosin, and meromyosin which are known as regulatory proteins. Actin and myosin proteins build filaments that are arranged in the myofibrils in a longitudinal manner. In addition to this, they assist in both cellular and noncellular movements.
Actin filaments are constituents of undifferentiated proteins organized into long spiral chains. Thin filaments of myofibrils accommodate 2F actins along with troponin and tropomyosin. Each of the F actin is the polymer of globular actin. 2F actins are twisted into a helix. The two filaments that arise from tropomyosin come in close contact with F-actins all around its length. The regulatory protein molecule troponin is allocated at regular intervals on the tropomyosin.
Myosin is a polymerized protein and has rough filaments. Meromyosin constituted the myosin. Troponin does not form the head of the myosin molecule
Hence the correct answer is Only (vi) .

Option ‘C’ is correct

Note:
Actin produce thin contractile filament within the muscle cells while myosin produces thick contractile filaments within muscle cells.