Tiêu đề Locomotion and Movement NEET EX-3 Solution fie.docx.pdf ✅

31 LOCOMOTION AND MOVEMENT EXERCISE – 3 : Achiever’s Section Muscles 1. Read the following statements and find out the incorrect statement (i) Movement is one of the significant features of living beings – both plants and animals. (ii) Streaming of protoplasm in the unicellular organisms like Amoeba is a simple form of movement (iii) Movement of cilia, flagella and tentacles are shown by Euglena, Paramecium and Hydra respectively (iv) Human beings can voluntarily move limbs, jaws, eyelids, tongue and ear pinna, etc. (v) Locomotion is done generally for search of food, shelter, mate, suitable breeding grounds and favorable climatic conditions or to escape from predators. (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (iv) and (v) Ans. (c) Sol. -Statement (iv) is incorrect. Human beings can move their limbs, eyelids, jaws. But they cannot normally move the ear pinna. - Statement (iii) is incorrect. In Paramecium cilia help in food gathering and movement. In Euglena flagella are used for movement. In Hydra tentacles are used for food capture and locomotion. 2. Which one of the following statements is incorrect? (a) Heart muscles are striated and involuntary. (b) The muscles of hands and legs are striated and voluntary. (c) The muscles located in the inner walls of alimentary canal are striated and involuntary (d) Muscles located in the reproductive tracts are unstriated and involuntary. Ans. (c) Sol. -The muscles in the alimentary canal are non-striated, spindle-shaped, involuntary, and are under ANS control. -Heart muscles are made up of cylindrical, branched striated cells that are involuntary and are not under the control of CNS. The muscles of legs and hands are striated muscles. They are voluntary muscles which can be moved as per the will. Muscles of the reproductive tract are generally non-striated, spindle shaped and involuntary, and are controlled by ANS. 3. Read the following statements and find out the incorrect statement (i) About 40-50% of the body weight of a human adult is contributed by muscles. (ii) Muscles have special properties like excitability, contractility, extensibility and elasticity. (iii)Based on their location, three types of muscles are identified: skeletal, smooth and cardiac (iv) Based on appearance, cardiac muscles are striated. They are involuntary in nature as the nervous system does not control their activity directly. (a) (ii) and (iii) (b) (i) and iii) (c) Only (i) (d) None of the above Ans. (d) Sol. -About 40-50 % of the body weight of a human adult is contributed by muscles. -Muscles have special properties like excitability, contractility, extensibility, and elasticity. -Based on their location, three types of muscles are identified: skeletal, smooth, and cardiac. -Based on appearance, cardiac muscles are striated. They are involuntary as the nervous system does not control their activity directly. 4. Cardiac muscles are different from that of skeletal muscles because the former are: (a) Striated but involuntary (b) Striated but voluntary (c) Non striated and involuntary (d) Smooth and striated Ans. (a) Sol. Cardiac muscles are striated but they are involuntary whereas the skeletal muscles are striated and voluntary in nature. 5. Which set clearly identifies the skeletal muscle?
30 LOCOMOTION AND MOVEMENT (a) Cylindrical, synctitial, unbranched (b) Spindle, unbranched, uninucleate (c) Cylindrical, striped, uninucleated (d) Cylindrical, striped, branched Ans. (a) Sol. Skeletal muscles are cylindrical, synctitial and unbranched. They are voluntary in nature and their nuclei are located at the periphery. Detailed Structure of Skeletal Muscles 6. Read the statements regarding muscle proteins. i Actin is a thin filament and is made up of two F-actins ii Complex protein tropomyosin is distributed at regular intervals on the troponin. iii Myosin is a thick filament which is also a polymerized protein. iv Globular head of meromyosin consists of light meromyosin (LMM) Of the above statements: (a) (i), (iii) and (iv) are correct (b) (i) and (iii) are correct (c) (i), (ii) and (iii) are correct (d) (i), (ii) and (iv) are correct Ans. (b) Sol. -Statement ii is incorrect. A complex protein named troponin is distributed at regular intervals over the tropomyosin. -Statement iv is incorrect. The globular head of meromyosin consists of heavy meromyosin. 7. Which of the following statements about the molecular arrangement of actin 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- actin are twisted into a helix. (iv) Two strands of tropomyosin (protein) lie in the grooves of F-actin. (v) Troponin molecules (complex proteins) are distributed at regular intervals on the tropomyosin. (vi) Troponin forms the head of the myosin-molecule. (vii) Myosin is a polymerized protein. (a) (i), (iii) and (vii) (b) (ii), (iv) and (v) (c) Only (vi) (d) Only (iii) Ans. (c) Sol. Statement (vi) is wrong. Troponin is a component of actin filament. It has three subunits named Troponin I, Troponin C and Troponin T. It is not a part of the myosin filament. Myosin head is made of heavy meromyosin (HMM). 8. Which of the following is correct about the given figure? (a) The length of the thick and thin myofilaments has changed (b) Length of both anisotropic and isotropic band has changed (c) The myosin cross bridges move on the surface of actin and the thin and thick myofilaments slide past each other (d) Length of the sarcomere remains same Ans. (c) Sol. - As shown in the figure, the myosin cross bridges move on the surface of actin and the thin and thick myofilaments slide past each other. -The length of the thick and thin myofilaments remain unchanged; they just slide over each other. -Length of the isotropic band has changed but that of the anisotropic band remains unchanged. -Length of the sarcomere changes. 9. Which of the following is true for the labelled parts (A, B, C, D) in the figure below?
31 LOCOMOTION AND MOVEMENT (a) A ------ Z-line --------located at the center of I –band (b) B ------- Thin filament--------occurs in A-band only (c) C-------- Thick filament ---------confined to I-band (d) D------H-zone --------- located at center of M-line Ans. (a) Sol. -The label A indicates Z-line. It is located at the center of I-band. -Label B is indicating thin filament. It occurs in A-band and also in I-band. -Label C is of thick filament. It is absent from the I-band. It is confined to A-band. -H zone is the central part of the thick filament. It is not overlapped by thin filaments. The M-line is located at the center of H-zone. 10. The skeletal muscle fibers will not show presence of H zone when (a) The central gap between actin filaments extending through myosin filaments in the A band is maximum. (b) Extension of myosin filaments in the central portion of the A band is minimum. (c) The myofibrils are absent in the central portion of A band. (d) The actin filaments forming the A band have slid to maximum possible extent leaving no gap. Ans. (d) Sol. The edges of thin filaments on either side of thick filament partially overlap the free ends of thick filament. This central part of thick filament which is not overlapping with thin filaments is called H zone. When there is maximum contraction of muscles, the gap between the actin filaments is completely filled. Hence, when the actin filaments forming the A band have slid to maximum possible extent there will be no H-zone present. 11. During muscular contraction, which of the following events occur? (i) H-zone disappears. (ii) A-band widens (iii)I-band reduces in width (iv) Width of the A-band is unaffected. (v) M-line and Z-line come closer. (a) (i), (ii) and (v) (b) (i), (iii), (iv) and (v) (c) (ii), (iv) and (v) (d) (i), (ii) and (iii) Ans. (b) Sol. The segment between two neighbouring Z lines is known as sarcomere. During muscular contraction, the surrounding of the Z line is the region of I band (thick filament- myosin), followed by A band which contains the entire single thick filament. Within the A band, the center region which is known as the H zone of thick filament has no actin. Within the H zone, a thin M line is formed by cross-connecting elements of the cytoskeleton. Muscle contraction is brought about by sliding movement of actin filament over myosin filament. When a muscle fibril contracts, its A band remains constant and the I band shortens. H zone also disappears. As the actin filament on both sides in each sarcomere overlap each other at M line, the M line and the Z line come closer. 12. Recognize the figure and choose the correct answer. (a) a-HMM, b-LMM, c-ATP binding sites, d-myosin binding sites (b) a- head, b-cross bridge, c-actin binding sites, d-ATP binding sites (c) a-head, b- cross arm, c-ATP binding sites, d-actin binding sites (d) a-head, b- cross arm, c-actin binding sites, d-ATP binding sites Ans. (d)
30 LOCOMOTION AND MOVEMENT Sol. The globular part of myosin is known as the head, which helps to form a cross-bridge by attaching with actin. The head and neck are together known as a cross arm. The topmost area on the head of the myosin is the actin-binding site, this site helps in the attachment of myosin to actin. ATP binding site is present anteriorly below the actin-binding site. This site attaches to ATP to form ADP. The energy released is used for the sliding of cross-bridges. 13. Read the given statement and select the correct option. Statement 1: A primary myofilament is composed of a bundle of rod-like molecules of a protein myosin. Statement 2: Myosin and actin together form a contractile apparatus. (a) Both statements 1 and 2 are correct and statement 2 is the correct explanation of statement 1. (b) Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1. (c) Statement 1 is correct and statement 2 is incorrect. (d) Both statement 1 and 2 are incorrect Ans. (b) Sol. There are two myofilaments that make up a muscle fibre. One is primary myofilament which is made up of myosin and other is secondary myofilament is made up of actin filament. Both actin and myosin are the contractile proteins Sliding Filament Theory 14. Which of the following options shows the correct order of some stages of muscle contraction from the beginning to the end of the process? (a) Stimuli, Neurotransmitter secretion, Release of Ca 2+ , Cross bridges formation, Excitation of T-system, Sliding of actin filaments (b) Stimuli, Neurotransmitter secretion, Excitation of T-system, Release of Ca 2+ , Cross bridges formation, sliding of actin filaments, ‘H’ band diminishes (c) Stimuli, Excitation of T-system, Neurotransmitter secretion, Cross bridges formation, sliding of actin filaments, ‘H’ band diminishes (d) Stimuli, Neurotransmitter secretion, Cross bridges formation, Excitation of T-system, Sliding of actin filaments Ans. (b) Sol. As per the sliding filament theory, following is the sequence of events during muscle contraction: -Stimuli: The stimulus generates an electrical impulse which arrives at the neuromuscular junction. -Neurotransmitter secretion: The synaptic vesicles release the neurotransmitters in the synaptic cleft. -Excitation of T-system: The T (tubular) system is activated as the neurotransmitter triggers the depolarization along the muscle membrane. -Release of Ca 2+: The flow ofCa 2+ through T tubules and sarcoplasmic reticulum results in increased Ca 2+ levels in the sarcoplasm. -Cross bridges formation: The binding of Ca 2+with troponin causes unmasking of myosin binding sites on actin. Cross bridge formation between the myosin and actin occurs. -Sliding of actin filaments: ATP hydrolysis provides energy for movement of cross bridges. It results in sliding of actin filaments. - ‘H’ band diminishes: As the actin filaments slide in, the H band separating the two adjacent actin filaments diminishes. 15. Which of the following options show the next stage of muscle contraction after the stage given in the question?