When Hb loads O2, what happens to its affinity for H+?

When hemoglobin (Hb) loads oxygen (O2), its affinity for hydrogen ions (H+) decreases. This phenomenon is part of what's known as the Bohr effect, where the binding of O2 to hemoglobin promotes the release of H+. As hemoglobin becomes saturated with oxygen in the lungs, it undergoes a conformational change that reduces its affinity for H+. This is advantageous because it facilitates the release of carbon dioxide (CO2) - which is carried by H+ ions in the blood - allowing for more efficient oxygen delivery to tissues. Consequently, decreased affinity for H+ when hemoglobin is oxygenated enables it to effectively transport oxygen while also regulating acid-base balance by minimizing CO2 binding during oxygen loading.