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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 (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 ...
The bicarbonate ion (hydrogencarbonate ion) is an anion with the empirical formula HCO − 3 and a molecular mass of 61.01 daltons; it consists of one central carbon atom surrounded by three oxygen atoms in a trigonal planar arrangement, with a hydrogen atom attached to one of the oxygens.
In renal compensation, plasma bicarbonate rises 3.5 mEq/L for each increase of 10 mm Hg in PaCO 2. The expected change in serum bicarbonate concentration in respiratory acidosis can be estimated as follows: [citation needed] Acute respiratory acidosis: HCO 3 − increases 1 mEq/L for each 10 mm Hg rise in PaCO 2.
Raised levels of acid bind to bicarbonate to form carbon dioxide through the Henderson-Hasselbalch equation resulting in metabolic acidosis. In these conditions, bicarbonate concentrations decrease by acting as a buffer against the increased presence of acids (as a result of the underlying condition).
The decreased bicarbonate that distinguishes metabolic acidosis is therefore due to two separate processes: the buffer (from water and carbon dioxide) and additional renal generation. The buffer reactions are: H + + HCO 3 − ↽ − − ⇀ H 2 CO 3 ↽ − − ⇀ CO 2 + H 2 O {\\displaystyle {\\ce {H+ + HCO3- <=> H2CO3 <=> CO2 + H2O}}}
The value measures the total dissolved Carbon dioxide (CO 2) in blood. It is determined by combining the Bicarbonate (HCO − 3) and the partial pressure of CO 2 multiplied by a factor which estimates the amount of pure CO 2 that is dissolved in its natural form (usually 0.03). [citation needed] One given reference range is 24–32 mEq/L. [1]
Accordingly, measurement of base excess is defined, under a standardized pressure of carbon dioxide, by titrating back to a standardized blood pH of 7.40. The predominant base contributing to base excess is bicarbonate. Thus, a deviation of serum bicarbonate from the reference range is ordinarily mirrored by a deviation in base excess.
Bicarbonate in the red blood cell (RBC) exchanging with chloride from plasma in the lungs. The underlying properties creating the chloride shift are the presence of carbonic anhydrase within the RBCs but not the plasma, and the permeability of the RBC membrane to carbon dioxide and bicarbonate ion but not to hydrogen ion.