Blood pH is normally regulated by the respiratory system to control the level of
ID: 499706 • Letter: B
Question
Blood pH is normally regulated by the respiratory system to control the level of CO2 and by the urinary system to control the levels of HCO3- and non volatile acids in the blood.
Given the overall reaction, CO2 + H2O H2CO3 HCO3- + H+, what effect would each of the following have on blood pH? Explain with LeChatliers principle.
a. Hyperventilating
b. Holding your breath for extended period of time.
c. Excessive ingestion of baking soda, HCO3-
d. Inhibiting renal carbonic anhydrase.
Mary also has an acid-base disturbance that is being compensated for with another body system. Identify the type of disturbance and trace out the physiological pathway responsible for the compensating action.
Explanation / Answer
a)Hyperventilating is a condition when the rate of CO2 exhalation exceeds its production in the body.This decreases CO2 concentration in the body.
CO2 is a reactant of the given reaction ,so if concentration of reactant decreases ,the equilibrium shifts backwards to compensate for the decrease.(Le Chatlier's principle) thereby forming lesser amounts of the products .As H+ is a product so its concentration decreases as well. pH=-log [H+]
So as [H+] decreases ,pH of blood increases.
b)Holding breath for extended period of time decreases the amount of CO2 exhaled so that its concentration increases in the body ,due to accumulation;
As CO2 is a reactant of the given reaction ,so if concentration of reactant increases ,the equilibrium shifts forward to compensate for the increase.(Le Chatlier's principle) thereby forming more products .As H+ is a product so its concentration increases as well. pH=-log [H+]
So as [H+] increases ,pH of blood decreases.
c)Excessive ingestion of baking soda, HCO3-
HCO3 - is a product of the rxn,so as the concentration of product increases ,the equilibrium shifts backwards to compensate for the increase.(Le Chatlier's principle) thereby forming more reactantss .As H+ is a product so its concentration decreases as well. pH=-log [H+]
So as [H+] decreases ,pH of blood increases.
d)Inhibiting renal carbonic anhydrase
Carbonic anhydrase is an enzymes that catalyses the above reaction.As it catalyses both forward and backward reaction at the same rate .So no change in concentration of reactants or products takes place .No change in [H+],so no change in pH
Acid -base equilibrium rxn-
H2CO3 HCO3- + H+ pka for this rxn=6.3
pH>pka, then only the given rxn occurs.
Disturbance :pH<pka [high H+ concentration]
physiological pathway responsible for the compensating action.-enzyme inhibitor for carbonic anhydrase is required to decrease the rate of the acid-base rxn.