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Multiple Choice
Which of the following structures is responsible for storing and releasing calcium ions in a skeletal muscle fiber?
A
Sarcoplasmic reticulum
B
Myofibril
C
Sarcolemma
D
T-tubule
Verified step by step guidance
1
Understand the role of calcium ions in muscle contraction: Calcium ions are essential for initiating the interaction between actin and myosin filaments, which leads to muscle contraction.
Identify the structure responsible for storing calcium ions: The sarcoplasmic reticulum is a specialized organelle in muscle cells that stores calcium ions and releases them when triggered by a signal.
Differentiate the other options: The myofibril is the contractile unit of the muscle fiber, the sarcolemma is the plasma membrane of the muscle cell, and the T-tubule is involved in transmitting the action potential deep into the muscle fiber.
Connect the sarcoplasmic reticulum to its function: When an action potential travels down the T-tubules, it triggers the sarcoplasmic reticulum to release calcium ions into the cytoplasm of the muscle cell.
Conclude that the sarcoplasmic reticulum is the correct answer because it is directly responsible for storing and releasing calcium ions in skeletal muscle fibers.