What is the specialized organelle in muscle cells that serves to sequester calcium?
Correct answer: D. Sarcoplasmic reticulum
- A. T-tubule
- B. Sarcolemma
- C. Sarcomere
- D. Sarcoplasmic reticulum
Explanation
Calcium diffusing in the cytoplasm between myosin and actin filaments of the muscle fibrils causes the filaments to slide into each other, triggering the contraction of the entire muscle fiber. The sarcoplasmic reticulum is a storage site for calcium within cells. Calcium is pumped into the sarcoplasmic reticulum by active transport and released in response to hormonal signals. A key to identifying the answer is to single out sarcoplasmic reticulum as the only organelle in the given options.
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About Support and Movement
Support and movement covers the axial and appendicular skeleton, bone structure, joints and the arrangement of skeletal muscles. Muscle contraction is explained through actin, myosin, sliding filaments, calcium ions and ATP, while arthritis is distinguished as a disorder of joints rather than a normal part of movement.
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