Calcium (Ca~2+) is an essential signalling molecule in many biological systems, and normal intracellular calcium levels at ～100 nM are 20 000-fold lower than the 2 mM concentration found extracellularly. Homoeostatic mechanisms are tightly controlled to Enable Ca~2+ to mediate a variety of cellular functions And to prevent susatained rises in intracellular calcium Concentration which result in cell death.
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