Is dihydrogen phosphate primarily an intracellular or extracellular buffer?

Dihydrogen phosphate (H2PO4-) functions primarily as an intracellular buffer due to its role in the regulation of intracellular pH. Within cells, the phosphate buffering system is crucial for maintaining a stable pH, especially in the context of cellular metabolism where various biochemical reactions produce acids that could lead to pH fluctuations. The intracellular concentration of phosphate species, including dihydrogen phosphate and its conjugate base, hydrogen phosphate (HPO4^2-), allows for effective buffering.

In contrast, while phosphate ions can also be found in the extracellular fluid, their concentrations there are significantly lower compared to other buffering systems, such as bicarbonate. The bicarbonate buffer system predominates in the extracellular space, particularly in the plasma. Therefore, while both environments may contain phosphate, it is the intracellular environment where dihydrogen phosphate serves its primary function as a buffer. This distinction is important for understanding acid-base balance in biological systems and how different buffers operate under varying conditions.