Human blood maintains a very tight pH range (usually 7.35-7.45). To do this it u

Question

Human blood maintains a very tight pH range (usually 7.35-7.45). To do this it uses the bicarbonate buffer system and its reversible reactions as shown below. Uncontrolled diabetes can result in ketoacidosis - a condition in which metabolic acids like beta-hydroxybutyrate (a ketone body) build up in the blood supply. Beta- hydroxybutyrate acid has a pKa well below that of physiological pH. A classic characteristic of ketoacidosis is deep and rapid breathing. Provide a biochemical rationale for why this occurs.

CO2 + H2O <-> H2CO3 <-> H+ + HCO-

Explanation / Answer

Deep and rapid breathing takes place only when the body needs oxygen or when it want to remove CO2. Given the bicarbonate buffer maintains the pH of the system. The whole reaction is an equilibrium. Beta hydroxy butyric acid has a lower pKa compared to physiological pH. Lower pKa means higher acidity or the more protons will be liberated from acid. If the proton concentration increases due to the acidity of beta hydroxy butyric acid, then the given buffer system's equilibrium will shift in such a way to reduce the proton concentration. This will lead to the formation of more carbonic acid in blood. Carbonic acid, a weak acid, is also in equilibrium with the carbon dioxide and water. Since the concentration of carbonic acid increases, the equilibrium will readjusted in such way that more amount of CO2 and water will be produced. So to remove this excess CO2, deep and rapid breathing is needed.

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