Muscle Contractility Questions and Answers

This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cell Motility – Muscle Contractility”.

1. Muscle cells are ___________
a) irregularly shaped
b) cylindrically shaped
c) extremely fragile
d) extremely labile
View Answer

Answer: b
Explanation: Muscle cells are cylindrically shaped, 10 to 100 μm thick and 100 mm long. Due to these distinctive properties a skeletal muscle cell is called muscle fiber.

2. Muscle cells are formed from the fusion of ___________
a) myoblasts
b) fibroblasts
c) mast cells
d) neurons
View Answer

Answer: a
Explanation: Muscle fibers contain many nuclei because each muscle fiber is a product of fusion of myoblasts. Myoblasts are premuscle cells in the embryo.

3. The striated appearance of muscle fibers is due to _______________
a) nucleus
b) sacromeres
c) sarcoma
d) myoblasts
View Answer

Answer: b
Explanation: Hundreds of thin, cylindrical strands called myofibrils. Each myofibril contains repeating contractile units, called sarcomeres. The sarcomeres exhibit a banding pattern giving the muscle cells a striated appearance.

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4. All skeletal muscles operate by _______________
a) shortening
b) exciting
c) firing
d) contracting
View Answer

Answer: a
Explanation: The skeletal muscles operate by the process of shortening, sacromeres are the units of shortening whose combined decrease in length account for decrease in length of entire muscle.

5. ________ of the sacromere remains unaffected during the muscle contraction.
a) H zone
b) A band
c) I band
d) H band
View Answer

Answer: b
Explanation: The A band of sacromeres remains constant in length whereas H and I bands decrease in length and disappear altogether.

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6. The “Sliding filament model of muscle contraction” was proposed in the year ____________
a) 1954
b) 1964
c) 1974
d) 1984
View Answer

Answer: a
Explanation: The “Sliding filament model of muscle contraction” was proposed in the year 1954 by two groups of British investigators, Andrew Huxley and Rolf Niedergerke, and Hugh Huxley and Jean Hanson.

7. According to “Sliding filament model of muscle contraction”, shortening of sacromeres results from sliding of the filaments.
a) True
b) False
View Answer

Answer: a
Explanation: According to the “Sliding filament model of muscle contraction” shortening of sacromeres results from sliding of the filaments one over the other.

8. Which of the following proteins are not found in muscle fibres?
a) keratin
b) actin
c) troponin
d) tropomyosin
View Answer

Answer: a
Explanation: The muscles fibers consist of actin, troponin and tropomyosin. All these aforementioned are motor proteins.

9. Each tropomyosin is associated with _______ subunits of actin subunits.
a) 2
b) 3
c) 7
d) 9
View Answer

Answer: c
Explanation: Tropomyosin is a 40 nm long elongated molecule and it fits into the grooves of within the thin filaments. Each tropomyosin is associated with 7 actin subunits.

10. Troponin is composed of _____ subunits.
a) 1
b) 2
c) 3
d) 4
View Answer

Answer: c
Explanation: Troponin is a globular protein found in muscle fibers. It consists of three subunits, each having a distinctive role in the overall function of the molecule.

11. Titin is the largest protein discovered till date.
a) True
b) False
View Answer

Answer: a
Explanation: Titin is an abundant protein found in skeletal muscles and is the largest protein discovered in any organism. The gene encoding for titin contains approximately 38000 amino acids.

12. Which of the following prevents sacromeres from pulling apart during muscle stretching?
a) titin
b) vimentin
c) myosin
d) actin
View Answer

Answer: a
Explanation: Titin prevents sacromeres from pulling apart during muscle stretching and maintains myosin filaments in their proper position.

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