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The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of carbonic acid (H 2 CO 3), bicarbonate ion (HCO − 3 ), and carbon dioxide (CO 2 ) in order to maintain pH in the blood and duodenum , among other tissues, to support proper metabolic function. [ 1 ]
With carbonic acid as the central intermediate species, bicarbonate – in conjunction with water, hydrogen ions, and carbon dioxide – forms this buffering system, which is maintained at the volatile equilibrium [3] required to provide prompt resistance to pH changes in both the acidic and basic directions.
Recall that the relationship represented in a Davenport diagram is a relationship between three variables: P CO 2, bicarbonate concentration and pH.Thus, Fig. 7 can be thought of as a topographical map—that is, a two-dimensional representation of a three-dimensional surface—where each isopleth indicates a different partial pressure or “altitude.”
These buffers include the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system. [7] Respiratory component: The second line of defense is rapid consisting of the control the carbonic acid (H 2 CO 3) concentration in the ECF by changing the rate and depth of breathing by hyperventilation or hypoventilation.
The regulation of H + ions and bicarbonate HCO − 3 is determined by the concentration of the two released within the urine. [1] These mechanisms of secretion and reabsorption balance the pH of the bloodstream. [1] A restored acid-base balanced bloodstream thus leads to a restored acid-base balance throughout the entire body.
In biochemistry and physiology, the name "carbonic acid" is sometimes applied to aqueous solutions of carbon dioxide. These chemical species play an important role in the bicarbonate buffer system, used to maintain acid–base homeostasis. [7]
For example, bicarbonate (HCO 3 −) does not have a transporter, so its reabsorption involves a series of reactions in the tubule lumen and tubular epithelium. It begins with the active secretion of a hydrogen ion (H +) into the tubule fluid via a Na/H exchanger: In the lumen The H + combines with HCO 3 − to form carbonic acid (H 2 CO 3)
Carbonic acid then spontaneously dissociates to form bicarbonate Ions (HCO 3 −) and a hydrogen ion (H +). In response to the decrease in intracellular pCO 2, more CO 2 passively diffuses into the cell. Cell membranes are generally impermeable to charged ions (i.e. H +, HCO 3 −) but RBCs are able to exchange bicarbonate for chloride using ...