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Multiple Choice
Which of the following is the site of calcium ion storage within muscle cells?
A
Mitochondria
B
T-tubules
C
Sarcolemma
D
Sarcoplasmic reticulum
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 calcium ion storage: The sarcoplasmic reticulum is a specialized organelle within muscle cells that stores and releases calcium ions when needed.
Differentiate the sarcoplasmic reticulum from other structures: The mitochondria are responsible for energy production, the T-tubules help propagate action potentials, and the sarcolemma is the plasma membrane of the muscle cell. None of these are directly involved in calcium ion storage.
Relate the sarcoplasmic reticulum to its function: During muscle contraction, the sarcoplasmic reticulum releases calcium ions into the cytoplasm, and during relaxation, it reabsorbs them to stop contraction.
Conclude that the sarcoplasmic reticulum is the correct answer based on its specialized role in calcium ion storage and regulation within muscle cells.