Question

How does an increase in the partial pressure of CO2 (e.g., at actively respiring tissues) affect hydrogen ion concentration [H+] and pH of blood? How do CO2 and H+ each affect hemoglobin's T to R transition, oxygen affinity, and oxygen delivery to the tissues?

Answer 1

Solution.

The increase of the  partial pressure of CO2 will increase the hydrogen ion concentration [H+] and decrease the pH of blood. As the human blood contains hydrocarbonate buffer system, the pH is affected according to Henderson–Hasselbalch equation:

, where pKa = 6.1 for carbonic acid and k = 0.03.

T to R state transition is accompanied bythe release of protons, so it would be inhibited in acidic medium. As hemoglobin moves into a more acidic region, its tendency to release oxygen increases. Hemoglobin responds to carbon dioxide with a decrease in oxygen affinity, thus facilitating the release of oxygen in tissues with a high CO₂ concentration.