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In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate [2]) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula H C O − 3. Bicarbonate serves a crucial biochemical role in the physiological pH buffering system. [3]
As calculated by the Henderson–Hasselbalch equation, in order to maintain a normal pH of 7.4 in the blood (whereby the pK a of carbonic acid is 6.1 at physiological temperature), a 20:1 ratio of bicarbonate to carbonic acid must constantly be maintained; this homeostasis is mainly mediated by pH sensors in the medulla oblongata of the brain ...
Aqueous carbon dioxide reacts with water to form carbonic acid which is very unstable and will dissociate rapidly into hydronium and bicarbonate. Therefore, in seawater, dissolved inorganic carbon is commonly referred to as the collection of bicarbonate, carbonate ions, and dissolved carbon dioxide (CO 2, H 2 CO 3, HCO − 3, CO 2− 3).
In chemistry, the term "carbonic acid" strictly refers to the chemical compound with the formula H 2 CO 3. Some biochemistry literature effaces the distinction between carbonic acid and carbon dioxide dissolved in extracellular fluid. In physiology, carbon dioxide excreted by the lungs may be called volatile acid or respiratory acid.
Sometimes the ratios of the concentrations are plotted rather than the actual concentrations. Occasionally H + and OH − are also plotted. Most often, the carbonate system is plotted, where the polyprotic acid is carbonic acid (a diprotic acid), and the different species are dissolved carbon dioxide, carbonic acid, bicarbonate, and carbonate.
The inorganic carbon species include carbon dioxide, carbonic acid, bicarbonate anion, and carbonate. [5] It is customary to express carbon dioxide and carbonic acid simultaneously as CO 2 *. C T is a key parameter when making measurements related to the pH of natural aqueous systems, [6] and carbon dioxide flux estimates.
The bicarbonate buffer, consisting of a mixture of carbonic acid (H 2 CO 3) and a bicarbonate (HCO − 3) salt in solution, is the most abundant buffer in the extracellular fluid, and it is also the buffer whose acid-to-base ratio can be changed very easily and rapidly. [15]
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.”