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Multiple Choice
In the structure of a skeletal muscle fiber, which organelle stores calcium ions (Ca2+) for release during muscle contraction?
A
Transverse (T) tubules
B
Mitochondria
C
Golgi apparatus
D
Sarcoplasmic reticulum
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Verified step by step guidance
1
Understand the role of calcium ions (Ca2+) in muscle contraction: Calcium ions are essential for initiating the interaction between actin and myosin filaments, which leads to muscle contraction.
Identify the organelles involved in muscle fiber structure: Key organelles include transverse (T) tubules, mitochondria, Golgi apparatus, and the sarcoplasmic reticulum.
Recall the function of each organelle: T tubules help propagate action potentials, mitochondria produce ATP, Golgi apparatus processes proteins, and the sarcoplasmic reticulum stores and releases calcium ions.
Focus on the sarcoplasmic reticulum: This specialized smooth endoplasmic reticulum in muscle fibers acts as a reservoir for Ca2+ ions, releasing them when the muscle fiber is stimulated to contract.
Conclude that the sarcoplasmic reticulum is the organelle responsible for storing calcium ions for release during muscle contraction.