Tag: muscles and their structure

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

The microfilaments of a muscle

  1. Are arranged in compartments known as sarcomeres

  2. Are composed of proteins known as actin and myosin

  3. Are the actual contractile elements of the fibre

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Myofilament is the filaments of myofibrils, constructed from proteins, principally myosin or actin.
  • They are made up of thick and thin myofilament, which helps to give it a striped appearance.
So, the correct option is 'all of the above'.

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

State whether the following statements are true or false.
Actin is actually a globular protein that assembles as a long beady structure consisting of two helical chains.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Skeletal muscle is composed of muscle fibres which have smaller units called myofibrils. There are three types of proteins make up each myofibril; they are contractile, regulatory and structural proteins. By contractile proteins, we mean actin (thin filament), a globular protein assembling with a long beady structure consisting chains and myosin (thick filament).

So, the correct option is 'True'.

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

The proteins found in the filaments of muscle fibres are

  1. Actin and myosin

  2. Myosin and elastin

  3. Actin only

  4. Myelin and tubulin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Skeletal muscle is composed of muscle fibres which have smaller units called myofibrils. There are three types of proteins make up each myofibril; they are contractile, regulatory and structural proteins. By contractile proteins, we mean actin (thin filament) and myosin (thick filament).

So, the correct option is 'actin and myosin'.

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

In the resting muscle fibre, tropomyosin partially covers

  1. calcium binding sites on troponin

  2. actin binding sites on myosin

  3. myosin binding sites on actin

  4. calcium binding sites on actin.
Reveal answer Fill a bubble to check yourself
C Correct answer
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).

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

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.

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

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

  3. only (vi)

  4. only (iii)
Reveal answer Fill a bubble to check yourself
A Correct answer
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).

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

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. 

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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).