How does decreased pH affect hemoglobin's affinity for oxygen?

• A. Increases affinity for oxygen
• B. No effect on hemoglobin
• C. Decreases affinity for oxygen
• D. Changes it to a liquid form

Answer: (C)

Decreased pH, or increased acidity in the blood, leads to a decrease in hemoglobin's affinity for oxygen. This phenomenon is part of the Bohr effect, which describes how carbon dioxide and pH levels influence the binding of oxygen to hemoglobin.

When the pH decreases, it indicates a higher concentration of hydrogen ions (H+), which binds to hemoglobin. This binding induces conformational changes in the hemoglobin molecule, which causes it to release oxygen more readily. The logic behind this response is physiological: in areas where metabolic activity is high (like active tissues), more carbon dioxide is produced, leading to lower pH and prompting hemoglobin to release oxygen where it's most needed.

The other options incorrectly describe the relationship between pH and hemoglobin's oxygen affinity. For instance, the notion that decreased pH would increase affinity contradicts the established understanding of the Bohr effect. Similarly, the idea that decreased pH has no effect is not accurate, as numerous studies have shown the sensitivity of hemoglobin to changes in pH. The mention of a physical transformation to a liquid form does not pertain to the biochemical interactions involved with hemoglobin and oxygen.