An advantage of carbonic acid as the main buffer is that it can provide H+ and HCO3- for buffering.

• A. It readily dissociates to release H+ and HCO3-
• B. It does not dissociate
• C. It provides H+ and HCO3- to buffer
• D. It cannot buffer pH

Answer: (C)

The bicarbonate–carbonic acid buffer works through the reversible dissociation of carbonic acid (H2CO3) into hydrogen ions and bicarbonate (HCO3−). In solution, CO2 from metabolism dissolves and becomes H2CO3, which can then split to yield H+ and HCO3−. This dual presence lets the system respond to changes in pH in both directions: if a base is added, H2CO3 donates a proton to neutralize OH−, forming more HCO3−; if an acid is added, HCO3− consumes a proton to form H2CO3, which is then converted to CO2 and water and expelled. The ability to supply both H+ and HCO3− makes this buffer effective over a range of disturbances and links buffering to respiratory regulation, allowing rapid adjustment as CO2 levels shift. That’s why providing both H+ and HCO3− is advantageous.