Topic summary
Inorganic phosphate
Extracted from the Wikipedia article Phosphate.
Biochemistry of phosphates
Inorganic phosphate is generally denoted Pi and at physiological (homeostatic) pH primarily consists of a mixture of HPO4 and H2PO4 ions. At a neutral pH, as in the cytosol (pH = 7.0), the concentrations of the orthophosphoric acid and its three anions have the ratios
![{\displaystyle {\begin{aligned}{\frac {[{\mathrm {H} {\vphantom {A}}_{\smash[{t}]{2}}\mathrm {PO} {\vphantom {A}}_{\smash[{t}]{4}}{\vphantom {A}}^{-}}]}{[{\mathrm {H} {\vphantom {A}}_{\smash[{t}]{3}}\mathrm {PO} {\vphantom {A}}_{\smash[{t}]{4}}}]}}&\approx 7.5\times 10^{4}\\[4pt]{\frac {[{\mathrm {HPO} {\vphantom {A}}_{\smash[{t}]{4}}{\vphantom {A}}^{2-}}]}{[{\mathrm {H} {\vphantom {A}}_{\smash[{t}]{2}}\mathrm {PO} {\vphantom {A}}_{\smash[{t}]{4}}{\vphantom {A}}^{-}}]}}&\approx 0.62\\[4pt]{\frac {[{\mathrm {PO} {\vphantom {A}}_{\smash[{t}]{4}}{\vphantom {A}}^{3-}}]}{[{\mathrm {HPO} {\vphantom {A}}_{\smash[{t}]{4}}{\vphantom {A}}^{2-}}]}}&\approx 2.14\times 10^{-6}\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/a7bfb55f5ed7d0ba3805ba68970255099eca8291)