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CBSE Questions for Class 11 Medical Biology Locomotion And Movement Quiz 11 - MCQExams.com
CBSE
Class 11 Medical Biology
Locomotion And Movement
Quiz 11
Repetitive muscular activity at moderate levels, such as weight training, can result in
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Denervation atrophy
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Mood swings
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Muscular hypertrophy
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A decline in health
Explanation
Muscular dystrophy is a collection of muscle-wasting conditions.
A lack of a protein called dystrophin is the main cause of muscular dystrophy.
So, the correct option is 'Muscular dystrophy'.
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-actins are twisted into a helix.
(iv) Two stands 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.
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(i), (ii) and (vi)
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(ii), (iv) and (v)
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Only (vi)
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Only (iii)
Explanation
Each actin filament is made of two F filamentous actions that helically wound each other.
Each F actin is a polymer of monomeric 'G' actions.
Two filaments of another protein, tropomyosin also run close to the 'F' actions throughout its length.
A complex troponin is distributed at regular intervals on the tropomyosin.
In the resting state, a subunit of troponin masks the active binding sites for myosin on the actin filaments.
Each myosin filament is a polymerized protein.
So, the correct answer is option C.
State whether the following statements are true or false.
Actin is present in thin filament.
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True
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False
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 'True'.
Each actin filament is made of
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2 'G' Actin molecules
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2 F Actin molecules
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1 F Actin molecules
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1 G Actin molecules
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'.
To treat myasthenia gravis,
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Acetylcholine esterase activity is inhibited
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Receptors on motor end plate are reduced
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Secretion from nerve terminals is reduced
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Secretion from nerve terminals is enhanced
Explanation
Myasthenia gravis is a disease caused due to the antibodies produced by an immune system that blocks or destroy the receptor sites for a neurotransmitter called acetylcholine. The enzyme esterase or acetylcholine esterase break the acetylcholine and deactivates the neurotransmitter to stop muscle activation.
During treatment of myasthenia gravis, it is prevented by using a chemical drug acetylcholinesterase inhibitor. These acetylcholinesterase inhibitors increase the amount of acetylcholine available and so help muscle activation and contraction.
So the correct option is 'Esterase activity is inhibited'.
Which of the following is a component of thin filaments of a sarcomere?
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Actin and myosin
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Troponin and actin
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Mysosin and troponin
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Troponin, tropomyosin, actin
Explanation
Myofibrils consists of two types of contractile proteins, namely thick filaments and thin filaments. Thick filaments is composed of myosin only. Whereas thin filaments is composed of actin, tropomyosin and troponin. The sliding of thin filaments over thick filaments results in the muscle shortening.
Thus, the correct answer is 'Troponin, tropomyosin, actin.'
Osteoporosis is commonly caused due to:
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Decreased level of progesterone
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Decreased level of oestrogen
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Increased level of progesterone
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Increased level of oestrogen
Explanation
Osteoporosis causes bones to become weak and brittle, so brittle that a fall or even mild stresses such as bending over or coughing can cause a fracture. Osteoporosis-related fractures most commonly occur in the hip, wrist, or spine. The main cause of osteoporosis is bone loss due to a drop in your body's estrogen levels. Estrogen is a hormone that helps build and maintain your bones.
So, the correct option is option B.
Ram rotates the arm and looks to his left. Which of his body parts help him to do so?
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Head and shoulder
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Shoulder only
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Shoulder and neck
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Neck only
Explanation
Rotation of the arm is made possible by the joint at the shoulder. The partial rotation of the head to look in both directions is due to the action of the neck. The head as such is not capable of movement.
Hence the correct option is C.
State whether this statement is true or false.
The bending of the arm to touch the shoulder with our fingers is due to the action of the shoulder.
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True
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False
Explanation
The given statement is false. The bending of the arm that allows us to do this particular action is due to the movement of the elbow joint and not the shoulder.
State whether the given statement is true or false.
If a scale is tied to the arm such that the centre of the scale is at the elbow, one can still bend his arm.
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True
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False
Explanation
When a scale is attached to the arm with its centre at the elbow, the arm cannot be bent. This is because the movement of the elbow is restricted in such a condition and the bending of arm requires the action of the elbow.
Hence the given statement is false.
Which best describes the fossil record?
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The fossil record cannot provide evidence of evolution.
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The fossil record provides evidence of a common ancestor to many species.
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The fossil record provides evidence that disputes the theory of evolution.
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The fossil record is inaccurate because scientists are not able to date fossils.
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