Question

How do bicarbonate ions play a role in regulating hemoglobins affinity for oxygen and carbon dioxide

Answer 1

As blood nears the lungs, the carbon dioxide concentration decreases, causing an increase in pH. This increase in pH increases hemoglobin's affinity for oxygen through the Bohr effect, causing hemoglobin to pick up oxygen entering your blood from your lungs so it can transport it to your tissues. In your tissues, by contrast, the increasing CO2 concentration drives a decrease in pH, which helps force hemoglobin to dump the oxygen it's carried from the lungs, so your cells can use it to break down sugars for energy. The pH-mediated change in affinity for oxygen helps hemoglobin act like a shuttle that picks up oxygen in the lungs and deposits it in the tissues where it will be needed.

When carbon dioxide is in the blood, it reacts with water to form bicarbonate (HCO3−) and hydrogen ions (H+). As the level of carbon dioxide in the blood increases, more H+is produced and the pH decreases. The increase in carbon dioxide and subsequent decrease in pH reduce the affinity of hemoglobin for oxygen. The oxygen dissociates from the Hb molecule, shifting the oxygen dissociation curve to the right.