Figure 1. Schematic diagram illustrating possible routes of CO₂ entry into the human erythrocyte and secondary transport processes.

CO₂ may enter the erythrocyte either by directly diffusing through the lipid bilayer or by passing through membrane proteins (aquaporin-1, HCO₃⁻–Cl⁻ transporter) which would function as gas channels. Once CO₂ has entered the erythrocyte, it will be hydrated by CAII bound to the carboxyl terminus of the HCO₃⁻–Cl⁻ transporter. Intracellular carbonic acid then dissociates into a proton and bicarbonate. Both reaction products can be eliminated from the intracellular space by specific transporters, the Na⁺-H⁺ exchanger and the HCO₃⁻–Cl⁻ transporter. These processes will further increase the entry of CO₂ and therefore intracellular acidification. Net proton fluxes may also be linked to anion exchange activity (unspecified anion exchange with substrates A₁⁻ and A₂⁻).