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Intracellular Calcium

Meaning

Intracellular calcium refers to the concentration of free calcium ions Ca2+ within the cytosol and membrane-bound organelles of a cell, such as the endoplasmic reticulum and mitochondria. This ion is not merely a structural component but functions as a ubiquitous and essential second messenger that mediates a vast array of cellular processes. Maintaining a precise, tightly regulated concentration gradient between the intracellular and extracellular spaces is vital for cell signaling, muscle contraction, hormone secretion, and gene expression. Dysregulation of this gradient is implicated in various pathological states, including excitotoxicity and cell death.