Biology Chapter 12 Entry test MCQs
51. Globular monomers are present in:
a. Troponin
b. Actin
c. Tropomyosin
d. Myosin
52. A muscle protein that has 3 polypeptides:
a. Troponin
b. Actin
c. Tropomyosin
d. Myosin
Mechanism of Skeletal Muscle Contraction
53. Cross bridges form between:
a. Calcium and sodium
b. Troponin and tropomyosin
c. Sarcolemma and sarcoplasmic reticulum
d. Actin filaments and myosin heads
54. When a muscle is at rest, what blocks myosin from hinding to actin?
a. Troponin
b. Tropomyosin
c. Sarcomere
d. Tubulin
55. All of the following are true regarding muscle contraction except:
a. Z-lines gets closer
b. I band shortens
c. M-line disappears
d. A band remains unchanged
56. Contractile protein of skeletal muscle cells involving ATPase activity is:
a. Troponin
b. Actin
c. Tropomyosin
d. Myosin
57. Which triggers the release of calcium ions from sarcoplasmic reticulum?
a. Sarcomere contraction
b. Formation of actin-myosin cross bridges
c. An increase in calcium ion concentration
d. An action potential
58. According to sliding filament theory, when muscle fibers are stimulated by nervous system, which of the following changes occurs?
a. H-zone becomes more visible
b. 1-bands shorten
c. A-bands shorten
d. Z-lines move further apart
59. A motor unit is made up of:
a. All the neurons going into an individual section of a body
b. All the muscle fibers within a given muscle
c. A fascicle and a nerve
d. A motor neuron and the muscle fibers it innervates
60. It acts as immediate source of energy for muscles contraction.
a. Fatty acids
b. ATP
c. Glycogen
d. Phosphocreatine
61. When muscle contracts, thick and thin filaments undergo:
a. Lengthening
b. Overlapping
c. Contraction
d. Shortening
62. The function of calcium ions in muscle contraction is to:
a. Aid in the transmission of nerve impulse
b. Bind to troponin molecule and cause them to move
c. Bind to tropomyosin molecule and cause them to form cross bridges
d. Polarize visible light
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