Bicarbonate buffer system

Carbon dioxide, a by-product of cellular respiration, is dissolved in the blood, where it is taken up by red blood cells and converted to carbonic acid by carbonic anhydrase. Most of the carbonic acid then dissociates to bicarbonate and hydrogen ions.

The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of carbonic acid (H2CO3), bicarbonate ion (HCO−
3), and carbon dioxide (CO2) in order to maintain pH in the blood and duodenum, among other tissues, to support proper metabolic function.[1] Catalyzed by carbonic anhydrase, 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:[2][3][4]

As with any buffer system, the pH is balanced by the presence of both a weak acid (for example, H2CO3) and its conjugate base (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 acidemia (pH < 7.35) and alkalemia (pH > 7.45) in the blood.[5]

  1. ^ Krieg, Brian J.; Taghavi, Seyed Mohammad; Amidon, Gordon L.; Amidon, Gregory E. (2014-11-01). "In Vivo Predictive Dissolution: Transport Analysis of the CO2, Bicarbonate In Vivo Buffer System" (PDF). Journal of Pharmaceutical Sciences. 103 (11): 3473–3490. doi:10.1002/jps.24108. hdl:2027.42/109280. ISSN 1520-6017. PMID 25212721.
  2. ^ Oxtoby, David W.; Gillis, Pat (2015). "Acid-base equilibria". Principles of Modern Chemistry (8 ed.). Boston, MA: Cengage Learning. pp. 611–753. ISBN 978-1305079113.
  3. ^ Widmaier, Eric; Raff, Hershel; Strang, Kevin (2014). "The kidneys and regulation of water and inorganic ions". Vander's Human Physiology (13 ed.). New York, NY: McGraw-Hill. pp. 446–489. ISBN 978-0073378305.
  4. ^ Meldrum, N. U.; Roughton, F. J. W. (1933-12-05). "Carbonic anhydrase. Its preparation and properties". The Journal of Physiology. 80 (2): 113–142. doi:10.1113/jphysiol.1933.sp003077. ISSN 0022-3751. PMC 1394121. PMID 16994489.
  5. ^ Rhoades, Rodney A.; Bell, David R. (2012). Medical physiology : principles for clinical medicine (4th ed., International ed.). Philadelphia, Pa.: Lippincott Williams & Wilkins. ISBN 9781451110395.