Final answer:
Hemoglobin functions as a pH buffer by binding to hydrogen ions after carbon dioxide enters the red blood cell, which stabilizes the blood's pH as part of the bicarbonate buffer system.
Step-by-step explanation:
Hemoglobin functions as a pH buffer in the blood by binding to hydrogen ions after carbon dioxide enters the red blood cell. The correct answer to the question is: c) Hemoglobin binds hydrogen ions after carbon dioxide enters the red blood cell
Carbon dioxide diffuses into red blood cells, where an enzyme called carbonic anhydrase quickly converts it into carbonic acid (H₂CO₃). This carbonic acid immediately dissociates into bicarbonate ions (HCO₃⁻) and hydrogen ions (H⁺), which can lower the pH of the blood. To prevent pH changes, hemoglobin in the red blood cells binds these free H⁺ ions, stabilizing the pH. This process is part of the bicarbonate buffer system. When blood reaches the lungs, the reverse process occurs: bicarbonate is reconverted into carbon dioxide, which is then exhaled, completing the exchange.