Question

Draw equations to show how carbon dioxide affects the blood concentration of H+ (and thus the ph) and the blood concentration of HCO-3 indicate the direction of change in these values if blood carbon levels were to rise

Use the equation of the above question to explain how hyperventilation and hypoventilation affect the blood ph

Answer 1

Explanation:

The equation that shows the equilibrium reaction of carbon dioxide in the blood is the following one:

CO₂ + H₂O   ↔   H₂CO₃   ↔   H⁺ + HCO₃⁻

This equation describes the bicarbonate buffer system which regulates the pH of the blood.

• During hypoventilation, the CO₂ produced by the cells through metabolism is not released fast enough, so CO₂ levels in the blood increase. In this situation, the equation shifts towards the right, and an excess of protons is produced, therefore decreasing the pH and causing acidosis.

• During hyperventilation the breathing is very rapid and CO₂ is exhaled from the body at a very fast rate. In this situation, the CO₂ levels in the blood decrease, the equation shifts towads the left and the concentration of H+ thus decreases, causing alkalosis.

Answer 2

Answer:

a) C02 +H20       ⇆          H2CO3    

                    Carbonic

                    anhydrase.

b) H2CO3            ⇄     H+    + HC03-

From (a) above the elevated rise in Carbondioxide levels of the blood leads to formation of hydrogen trioxocarbonate IV acid by the enzyme Carbonic anhydrase in the RBC cytoplasm. This raises the blood levels of hydrogen ions in the RBC, and therefore the blood  pH.  Since (pH = -log{H}) therefore Acidosis of blood occurs. However Heamoglobin mopped up the H+ in the blood ,  thereby releasing its binding oxygen molecules to form heamoglobinic acid. H+  + Hb   →   HHb. Thus heamoglobin  acted as buffer, reducing the acidosis.

The  reversible  breakdown  of H2CO3 to  H+ and HC03.(b, above)  from the rise in C02 , prompt the  moveement of HCO3- from the  RBC cytoplasm  into the blood plasma. it is carried into the alveoli of  lungs by the blood.  On reaching the lungs the hydrogencarbonate ions combine with Hydrogen ions to form H2CO3. The reverse of (a) above. The H2C03 is a weak acid, it thus breaks down and release CO2 in the lungs. Thus reducing the level of C02, and therefore acidosis of blood.

As a result of elevated rise in blood  CO2; equation b above shifts to the right; the circulatory regulatory centre in the medulla is stimulated. This cause  rapid formation of HC03- , and withdrawal from the RBC cytoplasm into the blood plasma en route the lungs. It  thus breakdown as explained above. The build up of CO2 in the lungs increases breathing  rate,(hyperventilation) and C02 is exhaled from the lungs,and the  blood pH is increase.

In case there is low ventilation(Hypoventialtion)  equation b above shifts to the left, HC03- ion  did not leave the blood but rather combine with Hyrogen ions to form H2C03.This raises acidity of the blood, decreasing the blood pH.