Tag: contractile protein

Questions Related to contractile protein

In the resting muscle fibre, tropomyosin partially covers

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. calcium binding sites on troponin

  2. actin binding sites on myosin

  3. myosin binding sites on actin

  4. calcium binding sites on actin.

Show answer
Correct Option: C
Explanation:

Tropomyosin is a protein found in the actin filaments in muscles. The molecule contains two elongated strands that run along the length of the filament. When the muscle is at rest, the tropomyosin molecule covers the binding site of the actin molecule, where interaction with myosin occurs, On contraction of the muscle, the tropomyosin is displaced by another protein, troponin, allowing the interaction of actin with myosin. So, the correct answer is (c).

Which of the following statements about the molecular arrangement of action and myosin in myofibrils is/are 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 stands of tropomysion (protein) lie in the grooves of F-actin.
(v) Troponin molecurles (complex proteins) are distributed at regular intervals on the tropomyosin.
(vi) Troponin forms the head of the myosin molecule.
(vii) The myosin is a polymerised protein.

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. (i), (ii) and (vi)

  2. (ii), (iv) and (v)

  3. only (vi)

  4. only (iii)

Show answer
Correct Option: A
Explanation:

Following are the incorrect statements about the molecular arrangement of actin and myosin in myofibrils:

(i) Each actin (thin filament) is made of 2F (filamentous) actins.
(ii) F - actin is the polymer of G (globular) actin.
(iii) Troponin forms the head of the myosin molecule.
So, the correct answer is (a).

Which of the following contractile proteins contributes 55% of muscle protein by weight ?

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. Tropomyosin

  2. Troponin

  3. Myosin

  4. Actin

Show answer
Correct Option: C
Explanation:
Myosin is the protein that makes up the thick filaments and it comprises approximately 50-55% of the muscle protein by weight.
So, the correct answer is 'Myosin'.

Consider the following four statements (i) - (iv) and select the correct option.
(i) Actin is present in thin filament.
(ii) H-zone of striated muscle fibre represents both thick and thin filaments.
(iii) There are 11 pairs of ribs in man.
(iv) Sternum Is present on ventral side of the body. 

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. (i) F (ii) F (iii) T (iv) F

  2. (i) F (ii) F (iii) F (iv) T

  3. (i) T (ii) F (iii) F (iv) F

  4. (i) T (ii) F (iii) T (iv) F

Show answer
Correct Option: C
Explanation:

(i) Actin is present in thin filament - True

(ii) H-zone of striated muscle fibre represents both thick and thin filaments - False
(iii) There are 11 pairs of ribs in man - False
(iv) The sternum is present on the ventral side of the body - False
So, the correct answer is (c).

The linear protein that has catalytic function is _____________.

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. actin

  2. collaagen

  3. mysoin

  4. trypsin

Show answer
Correct Option: A
Explanation:
Actin usually exists as the globular monomer of G-actin and also as a polymer of F-actin. This F-actin is a linear chain of subunits of G-actin.
So, the correct answer is 'actin'.

Each actin filament is made of

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. 2 'G' Actin molecules

  2. 2 F Actin molecules

  3. 1 F Actin molecules

  4. 1 G Actin molecules

Show answer
Correct Option: B
Explanation:

Actin is the protein which helps in the muscle contraction. It present in two forms G actin (globular actin) and F actin (filament actin). In muscles, actin filament is formed by the two long strand of bead-like twisted actin molecule. 

So, the correct answer is '2 F Actin molecules'.

Contractile unit of muscle fibres is

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. Muscle fibre

  2. Sacromere

  3. Myofibril

  4. Sacrosome

Show answer
Correct Option: B
Explanation:

The entire cross section of the muscle fibre is taken up by long, cylindrical strands of contractile proteins called myofibrils. One myofibril is divided into segments called sarcomeres. These are the contractile units of a muscle. A dark stripe called a Z disc marks the ends of one sarcomere and the beginning of the next.

Contractile proteins include:

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. Troponin

  2. Tropomyosin

  3. Actin and myosin

  4. All the three

Show answer
Correct Option: C
Explanation:

The main components of protein in muscle is actin and myosine that form thin and thick fibers respectively.


The troponin and tropmyosine come under the category of regulatory proteins that regulate the process of muscle contraction.

for example troponin binds with tropomysosine to inhibit actin and myosine interaction during relaxation stage.

Hence the correct answer is (C). 

The important muscle proteins that help in movement are

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. Actin and myosin

  2. Tropomyosin

  3. Troponin

  4. All of these

Show answer
Correct Option: D
Explanation:

Actin and myosin are the structural filaments that play the main role in muscle contraction by sliding filament theory.

Troponin and tropomyosin are the regulatory proteins that regulate the rate of attachment of myosin heads to actin. Hence they also play an important role in muscle contraction and its movement.
Troponin regulate availability of active sites of actin by attaching with Ca++
So the correct option is D.

Actin is present in thin filament.

zoology locomotion and movement contractile protein structure of muscle muscles and their structure

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Actin is the thin filaments of the muscles. They are a polymer of G-actin monomers arranged in chains and two such chains are wound in a helix. So, the given statement is true.