Q18.183CP - Chemistry: Molecular Nature Of Matter And Change

Question

Hemoglobin (Hb) transports oxygen in the blood:

${\mathbf{\text{HbH}}}^{\mathbf{\text{ + }}}{\mathbf{\text{(aq) + O}}}_{\mathbf{\text{2}}}{\mathbf{\text{(aq) + H}}}_{\mathbf{\text{2}}}{\mathbf{\text{O(l)nHbO}}}_{\mathbf{\text{2}}}{\mathbf{\text{(aq) + H}}}_{\mathbf{\text{3}}}{\mathbf{\text{O}}}^{\mathbf{\text{ + }}}\mathbf{\text{(aq)}}$

In blood, ${\mathbf{\text{H}}}_{\mathbf{\text{3}}}{\mathbf{\text{O}}}^{\mathbf{\text{ + }}}$ is held nearly constant at ${\mathbf{\text{4×10}}}^{\mathbf{\text{ - 8}}}\mathbf{\text{M}}$ .

(a) How does the equilibrium position change in the lungs? 

(b) How does it change in O2-deficient cells? 

(c) Excessive vomiting may lead to metabolic alkalosis, in which [${\mathbf{\text{H}}}_{\mathbf{\text{3}}}{\mathbf{\text{O}}}^{\mathbf{\text{ + }}}$] in blood decreases. How does this condition affect the ability of Hb to transport ${\mathbf{\text{O}}}_{\mathbf{\text{2}}}$ ?

 (d) Diabetes mellitus may lead to metabolic acidosis, in which [${\mathbf{\text{H}}}_{\mathbf{\text{3}}}{\mathbf{\text{O}}}^{\mathbf{\text{ + }}}$] in blood increases. How does this condition affect the ability of Hb to transport ${\mathbf{\text{O}}}_{\mathbf{\text{2}}}$?

Step-by-Step Solution

Answer

a) The reaction will shift to the right

b) The reaction will shift to the left

c) During alkalosis, it is easier for Hb to transport oxygen

d) During acidosis, it is more difficult for Hb to transport oxygen.

Step 1: To find how does the equilibrium position change in the lungs

${\text{HbH}}^{\text{ + }}{\text{ + O}}_{\text{2}}{\text{ + H}}_{\text{2}}\text{O}\rightleftharpoons {\text{HbO}}_{\text{2}}{\text{ + H}}_{\text{3}}{\text{O}}^{\text{ + }}$

Step 2: To find How does it change in O2-deficient cells

(b) in ${{\text{O}}_{\text{2}}}^{\text{ - }}$ deficient cells

With deficient supply of oxygen in the reactant side, the reaction will shift to the left. This is according to Le Chatelier's principle. The lack of oxygen in the reactant disturbs the equilibrium and will produce adequate amount of oxygen to maintain a new equilibrium.

Hence the reaction will shift to the left

Step 3: During alkalosis

(c) 

During alkalosis, the $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in blood decreases. With deficient $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in the product, the reaction will shift to the right As the $\left[{\text{H}}_3{\text{O}}^{+}\right]$ increase during the shift in reaction, the $\left[{\text{HbO}}_2\right]$ also increases. The oxygen binds to the haemoglobin and will be ready for transport. 

Therefore during alkalosis, it is easier for Hb to transport oxygen

Step 4: During acidosis

(d) 

During acidosis, the $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in blood increases. With abundant $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in the product, the reaction will shift to the left. As the $\left[{\text{H}}_3{\text{O}}^{+}\right]$ is being consumed during the shift in reaction to produce the left side products, $\left[{\text{HbO}}_2\right]$ also increases. The oxygen that binds to the hemoglobin for transport will decrease. 

Therefore during acidosis, it is more difficult for Hb to transport oxygen.