Intracellular pH

Intracellular pH (pH_i) is the measure of the acidity or basicity (i.e., pH) of intracellular fluid. The pH_i plays a critical role in membrane transport and other intracellular processes. In an environment with the improper pH_i, biological cells may have compromised function. Therefore, pH_i is closely regulated in order to ensure proper cellular function, controlled cell growth, and normal cellular processes. The mechanisms that regulate pH_i are usually considered to be plasma membrane transporters of which two main types exist — those that are dependent and those that are independent of the concentration of bicarbonate (HCO⁻
₃). Physiologically normal intracellular pH is most commonly between 7.0 and 7.4, though there is variability between tissues (e.g., mammalian skeletal muscle tends to have a pH_i of 6.8–7.1). There is also pH variation across different organelles, which can span from around 4.5 to 8.0. pH_i can be measured in a number of different ways.