THE CELL
CELL COMMUNICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Calcium ions are actively imported from the cytoplasm into the ER.
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Calcium levels in the blood or other body fluids are extremely low.
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Calcium cannot enter the plasma membrane through ion channels.
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Calcium concentration is kept low in the cytoplasm because of its high usage level.
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Detailed explanation-1: -C-cAMP. What explains the increased concentration of Ca++ in the ER? A-Calcium ions are actively imported from the cytoplasm into the ER.
Detailed explanation-2: -A high concentration of Ca2+ is maintained in the ER lumen by a member of the sarcoplasmic endoplasmic reticulum calcium ATPase family of Ca2+-ATPases that pump Ca2+ into the ER, counterbalancing a leak of Ca2+ ions through the ER membrane into the cytoplasm (27).
Detailed explanation-3: -Cytosolic Ca2+ entry into the ER is mediated through the SERCA pump, a Ca2+ ATPase that transfers Ca2+ from the cytosol to the SR/ER lumen via ATP hydrolysis.
Detailed explanation-4: -Which of the following substances acts to increase the release of Ca2+ from endoplasmic reticulum ? Inositol triphosphate (IP3) and diacylglycerol (DAG) are second messengers for G protein coupled receptors. IP3 stimulates release of calcium from endoplasmic reticulum.