Multiple Choice
When calcium binds to troponin, what happens to tropomyosin?
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15. Cytoskeleton and Cell Movement
Muscle Contractions
Multiple Choice
In the context of muscle contractions, the contractile unit of a muscle cell is the:
A
Sarcoplasmic reticulum
B
Transverse (T) tubule
C
Myofibril
D
Sarcomere
Verified step by step guidance1
Understand the structure of a muscle cell, which includes components such as the sarcoplasmic reticulum, transverse (T) tubules, myofibrils, and sarcomeres.
Recognize that the sarcoplasmic reticulum is responsible for storing and releasing calcium ions, which regulate muscle contraction but is not the contractile unit itself.
Know that transverse (T) tubules help propagate action potentials into the muscle fiber but do not directly contract.
Identify that myofibrils are long, cylindrical structures within muscle cells composed of repeating units called sarcomeres.
Conclude that the sarcomere is the fundamental contractile unit of a muscle cell, defined by the arrangement of actin and myosin filaments that slide past each other during contraction.
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