alleryStart learning →The specialized smooth ER of muscle cells stores which ion?
ACalcium ions
BSodium ions
CChloride ions
DHydrogen ions
Answer & Solution
Correct answer: A. Calcium ions
1. In muscle cells the smooth ER takes a specialized form called the sarcoplasmic reticulum.
2. Its job is the storage of calcium ions.
3. Those stored calcium ions are needed to trigger the coordinated contractions of the muscle cells.
4. Storage of calcium is already listed among the general functions of the smooth ER, so the specialization is a sharpened version of it.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 4 "Cell Structure", section 4.4 The Endomembrane System and Proteins_
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