Question

2. What the mechanisms of affecting Hb (hemoglobin) affinity to O2 -- by O2, CO2, CO, H+? Please explain in detail.

Answer 1

Increase in concentration of O2, will increase the affinity of hemoglobin to O2. Here, O2 is substrate and hemoglobin is the enzyme molecule. More substrate , more binding of O2 to hemoglobin.

Increase in CO2 concentration decreases the affinity , because of the increase in H+ ion concentration.

CO2 combines with H2O forming H2CO3 (carbonic acid). Carbonic acid is unstable compound and it immediately dissociates in to H+ and HCO3- ions. So more CO2 dissolving in the plasma, more H+ ions are released. Decrease in pH (acidic) will reduce the affinity of hemoglobin to O2.

Increase in CO concentrations will decrease the affinity of hemoglobin to O2. This is because hemoglobin forms a permanent compound with CO forming carbooxy hemoglobin. Because it forms a permanent compound with hemoglobin, there are less hemoglobin molecules to bind with O2.

Increase in H+ ion concentration will decrease the O2 binding capacity of hemoglobin. So O2 is released from oxyhemoglobin once H+ concentration increases. H+ ions attach to amino acids of the protein and change the shape of the protein in hemogobin. Such a protein will not be able to hold O2. That is why it releases O2.