Bicarbonate buffer system

The bicarbonate buffer system is an <a href="/facts/Acid%E2%80%93base_homeostasis/y4U6UENE">acid-base homeostatic</a> mechanism involving the balance of <a href="/facts/Carbonic_acid/fjjVAhwt">carbonic acid</a> (H2CO3), <a href="/facts/Bicarbonate/zzSVVAl1">bicarbonate ion</a> (HCO−3), and <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> (CO2) in order to maintain <a href="/facts/PH/RnSv8D7y">pH</a> in the <a href="/facts/Blood/03zEulkj">blood</a> and <a href="/facts/Duodenum/IAIgHBmq">duodenum</a>, among other tissues, to support proper <a href="/facts/Metabolism/WxDrm8k5">metabolic</a> function. Catalyzed by <a href="/facts/Carbonic_anhydrase/je7bk6fk">carbonic anhydrase</a>, carbon dioxide (CO2) reacts with water (H2O) to form carbonic acid (H2CO3), which in turn rapidly dissociates to form a bicarbonate ion (HCO−3 ) and a hydrogen ion (H+) as shown in the following reaction:

C
            
              O
              
                2
              
            
            +
            
              H
              
                2
              
            
            O
            ⇄
            
              H
              
                2
              
            
            C
            
              O
              
                3
              
            
            ⇄
            H
            C
            
              O
              
                3
              
              
                −
              
            
            +
            
              H
              
                +
              
            
          
        
      
    
    {\displaystyle {\rm {CO_{2}+H_{2}O\rightleftarrows H_{2}CO_{3}\rightleftarrows HCO_{3}^{-}+H^{+}}}}

As with any <a href="/facts/Buffer_solution/zrLz9eaa">buffer</a> system, the pH is balanced by the presence of both a <a href="/facts/Weak_acid/vJ4rj6Lu">weak acid</a> (for example, H2CO3) and its <a href="/facts/Conjugate_acid/hohgQ07M">conjugate base</a> (for example, HCO−3) so that any excess acid or base introduced to the system is neutralized.
Failure of this system to function properly results in acid-base imbalance, such as <a href="/facts/Acidemia/hmfAo1uR">acidemia</a> (pH < 7.35) and <a href="/facts/Alkalemia/SoUSH8No">alkalemia</a> (pH > 7.45) in the blood.

Bicarbonate buffer system open-in-new

Bicarbonate buffer system