that can act as an acid or as a base, depending on pH of the solution. At high pH, it dissociates significantly into the carbonate ion (CO₃^2-):
:HCO₃^- ? CO₃^2- + H⁺
:K_a2 = 4.69 × 10^-11 mol/L; pK_a2 = 10.329

In organisms, carbonic acid production is catalysed by the enzyme known as carbonic anhydrase.