Bohr Effect and pH Influence on Hemoglobin

Steps:

• Increased CO2 in blood reacts with water to form carbonic acid via carbonic anhydrase.
• Carbonic acid dissociates, releasing H+ ions and increasing blood acidity (lowering pH).
• Higher H+ concentration binds to hemoglobin, reducing its affinity for oxygen.
• This facilitates oxygen unloading in tissues, shifting the oxyhemoglobin dissociation curve rightward.

Why D is correct:

• The Bohr effect states that increased H+ (from CO2) decreases hemoglobin's oxygen affinity, promoting dissociation as per the equilibrium shift in hemoglobin-oxygen binding.

Why the others are wrong:

• A: Breathing rate changes are a separate ventilatory response, not the direct mechanism for curve shift.
• B: CO2 does not displace oxygen; it indirectly affects binding via pH alteration.
• C: Alveolar diffusion rates influence gas exchange but not hemoglobin's oxygen affinity.

Final answer: D