Biology · General Awareness

Muscle Biology

798 Questions

Muscle biology covers the structures, functions, and contraction mechanisms of skeletal, cardiac, and smooth muscles. Test questions target filaments, stimuli, and specific muscle roles. A clear understanding helps secure marks in biology sections.

Skeletal muscle controlCardiac muscle propertiesMuscle contraction mechanismActin and myosin filamentsMuscle functions

Muscle Biology Questions

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

Each actin filament is made of

  1. 2 'G' Actin molecules

  2. 2 F Actin molecules

  3. 1 F Actin molecules

  4. 1 G Actin molecules
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.

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

Contractile unit of muscle fibres is

  1. Muscle fibre

  2. Sacromere

  3. Myofibril

  4. Sacrosome
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Contractile proteins include:

  1. Troponin

  2. Tropomyosin

  3. Actin and myosin

  4. All the three
Reveal answer Fill a bubble to check yourself
C Correct answer
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). 

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

The important muscle proteins that help in movement are

  1. Actin and myosin

  2. Tropomyosin

  3. Troponin

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

The monomeric actin is called as

  1. F- actin

  2. M- actin

  3. G- actin

  4. N- actin
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Actin is the thin filament of the muscles. It is a polymer made of many monomers. The monomers of actin are globular in shape and hence called Globular-actin or G-actin. Monomers together form straight chains of polymer action. The polymer action is called F-actin.

So the correct option is C.

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

In a muscle fibre

  1. Sacrolemma is connective tissue holding the myofibrils together

  2. T system contains calcium storage sacs

  3. Both filaments have cross-bridges

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Terminal cisternae are enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubule because terminal cisternae ensure rapid calcium delivery, they are well developed in muscles that contract quickly such as fast-twitch skeletal muscle.
So, the T system contains calcium storage sacs.
Multiple choice zoology skeleton and movements contractile protein structure of muscle muscles and their structure

Actin binding sites are located over

  1. Troponin

  2. Tropomyosin

  3. Meromyosin

  4. Creatnine

  5. Both A and B
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • The myofibril is composed of two types of filaments. They are thick filament(Myosin) and Thin filament(Actin).
  • Increase in Ca++ level leads to the binding of calcium with a subunit of troponin i.e troponin-C on actin filaments and thereby remove the masking of active sites for myosin. Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
  • Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins constitute one thick filament. Each meromyosin has the globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.
  • Hence actin binding sites are located over meromyosin'.
  • So, the correct answer is 'Meromyosin'.