CBSE Questions for Class 11 Medical Biology Locomotion And Movement Quiz 6 - MCQExams.com

•  A neural signal reaching this junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm
  
• Active sites for myosin are present on actin which are masked by troponin-C in resting state. When Ca++ level increases it leads to the binding of calcium with a subunit of troponin i.e Troponin-C on actin(thin) 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. 
• This pulls the attached actin filaments towards the centre of ‘A’ band.
  
• The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. The myosin, releasing the ADP and P1 goes back to its relaxed state. Hence Ca$$^{2+}$$ is required for muscle contraction and nerve impulse transmission.
• So, the correct answer is 'Ca 2+'.

• Myofibril is made up of two types of filaments.They are thin filament(actin) and thick filament(myosin).
  
• Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length. A complex protein Troponin is distributed at regular intervals on the tropomyosin.
  
• Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins, constitute one thick filament. Globular head of meromyosin consists of Heavy meromyosin (HMM).
  
• So, the correct answer is 'i, ii and iii are correct'

• The myofibril is composed of two types of filaments. They are thick filament (Myosin) and Thin filament (Actin).
  
• Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length. A complex protein Troponin is distributed at regular intervals on the tropomyosin. In the resting state tropomyosin partially covers myosin binding site on 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.
• Hence In a resting muscle fibre, tropomyosin partially covers myosin binding sites on actin.
• So, the correct answer is 'Myosin binding sites on actin'.

• Muscular dystrophy is a group of inherited muscle diseases in which muscle fibers are unusually susceptible to damage.
  
• It is characterized by progressive skeletal muscle degeneration, defects in muscle proteins and the death of muscle cell and tissue.
• Hence progressive degeneration of skeletal muscle, mostly due to genetic disorder occurs in muscular dystrophy.
• So, the correct answer is 'Muscular dystrophy'.

• Active sites for myosin are present on actin which are masked by troponin-C in resting state. when  Ca++ level increases it leads to the binding of calcium with a subunit of troponin i.e Troponin-C on actin(thin) 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. 
• This pulls the attached actin filaments towards the centre of ‘A’ band.
  
•  The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.  The myosin, releasing the ADP and P1 goes back to its relaxed state.
• Hence During contraction of muscles Ca ++ attaches to Troponin -C.
• So, the correct answer is 'Troponin-C'
  
  

• Joints are points of contact between bones, or between bones and cartilages.
  
• A suture is a type of fibrous joint that is only found in the skull. The skull bones are joined by the sutures.
• Parietal bone and temporal bone are skull bones.
• Hence parietal bone and temporal bone of skull are joined by fibrous joint.
• So, the correct answer is 'Parietal bone and temporal bone of skull are joined by fibrous joint'.

• Autoimmune diseases are a group of disorders in which tissue injury is caused by humoral(autoantibodies)or cell-mediated(by autoreactive T cells) immune response to self-antigens.
  
• Myasthenia gravis is caused by an autoantibody against muscle antigen and acetylcholine receptor antigen.
  
• Myasthenia gravis is characterized by increased muscular weakness the make one fatigue. speaking, breathing and talking becomes tired some. Hence myasthenia gravis is an example of autoimmune disease.
  
• So, the correct answer is 'Autoimmune disease'.
  

• Joints are points of contact between bones, or between bones and cartilages.
  
• Synovial joints are characterized by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones. These joints help in locomotion and many other movements.
• The synovial cavity is covered by the synovial membrane which secretes a watery fluid called synovial fluid for the lubricating and cushioning joint.
• So, the correct answer is 'Synovial membrane'.

• Active sites for myosin(Thick filament) are present on actin which are masked by troponin in resting state. when  Ca++ level increases it leads to the binding of calcium with a subunit of troponin on actin(thin) 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. 
• This pulls the attached actin filaments towards the centre of ‘A’ band.
•  The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.
• magnesium acts as a natural calcium blocker to help muscles relax. Hence Mg ion is not involved in the muscular contraction but it is involved in muscle relaxation by blocking calcium ions.
• So, the correct answer is 'Mg'

• Myofibril is made up of two types of filaments. They are thick filament (myosin) and thin filament (actin). Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments respectively
  
• Each myosin (thick) filament is a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament.
  
• Hence myosin is the thick filament of muscle.
• So, the correct answer is 'Myosin'.

• Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called Meromyosins constitute one thick filament.
•  Each meromyosin has two important parts, a globular head(a) with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The HMM component, i.e.; the head and short arm projects outwards at regular distance and angle from each other from the surface of a polymerized myosin filament and is known as the cross arm(b).
  
•  The globular head has an active ATPase enzyme(d) and has binding sites for ATP and active sites for actin(c). 
• So, the correct answer is 'a - head, b - cross arm, c - actin binding site, d - ATP binding site'

• Skeletal muscle fiber is made up of two types of filaments. They are thick filament(myosin) and thin filament(actin). 
  
• Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins.
  
• Hence monomeric actin is known as G-actin.
• So,the correct answer is 'G-actin'.

• Skeletal muscle fiber is made up of two types of filaments. They are thick filament (myosin) and thin filament (actin). Contraction of a muscle fiber takes place by the sliding of the thin filaments over the thick filaments.
  
• Myosin (thick) filament is also a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament. 
  
• Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length. A complex protein troponin is distributed at regular intervals on the tropomyosin.
  
• Hence, the important muscles proteins that help in the movement are actin and myosin, troponin and tropomyosin.
• So, the correct answer is 'All of the above'.

• Neurotransmitter acetylcholine generates an action potential in the sarcolemma causing the release of calcium ions into the sarcoplasm from the sarcoplasmic reticulum.
• The sarcoplasmic reticulum acts as a reservoir for calcium ions in muscle cells. 
  
• When $$Ca^{++}$$ level increases it leads to the binding of calcium with a sub-unit of troponin on actin(thin) filaments and thereby activating the movement.

$$\textbf{Correct option: (B)}$$

$$\textbf{Solution:}$$

$$\textbf{Option (A):}$$

$$\textbf{Option (B):}$$

$$\bullet$$ It leads to decreased bone density and bone becomes weak and fragile.

$$\textbf{Option (C):}$$

$$\textbf{Option (D):}$$