Carbonic acid equilibrium (None)

The carbonic acid equilibrium describes the reversible reactions between dissolved carbon dioxide (CO₂), carbonic acid (H₂CO₃), bicarbonate ion (HCO₃⁻), and protons (H⁺) in aqueous solutions, especially within biological systems. This system is the foundation of the bicarbonate buffer system, the principal mechanism for maintaining acid–base homeostasis in blood and tissues. In the body, carbonic acid is rapidly formed from dissolved CO₂ and water, a reaction enormously accelerated by the enzyme carbonic anhydrase. H₂CO₃ then partially dissociates, yielding bicarbonate and protons, according to the reactions: CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻. The equilibrium is essential for efficient CO₂ transport from tissues to lungs, acid-base regulation, and rapid physiological buffering. While the carbonic acid equilibrium itself is not a direct therapeutic target, its dynamics are crucially determined by enzymes and transporters (such as carbonic anhydrase), which are pharmacological targets for modulating acid–base physiology or treating related diseases. Key caveat: The term "carbonic acid equilibrium" does not denote a discrete molecule, receptor, or gene product. It is a physicochemical concept describing the equilibrium among molecular species (CO₂, H₂CO₃, HCO₃⁻, H⁺). For therapeutic targeting or clinical diagnostics, the relevant molecular targets are enzymes (notably, various carbonic anhydrases) or transporters that mediate this equilibrium—not the equilibrium state itself.

Other names

Carbon dioxide–bicarbonate equilibriumBicarbonate buffer systemCarbonic acid–bicarbonate equilibriumCO₂/H₂CO₃/HCO₃⁻ system

Not applicable for the equilibrium itself. For modulating enzymes (e.g., carbonic anhydrase inhibitors): Inhibition of carbonic anhydrase, thus altering the rate at which CO₂ and water interconvert with carbonic acid, bicarbonate, and protons.