Answer
Effect of CO₂ Concentration on Oxygen Affinity (Bohr Effect)
✔ Correct Answer: Decreases hemoglobin’s oxygen affinity
The Bohr effect describes how increasing carbon dioxide (CO₂) concentration or decreasing pH (more H⁺ ions) causes hemoglobin to reduce its affinity for oxygen.
- Increased CO₂ leads to the formation of carbonic acid (H₂CO₃), which dissociates into H⁺ and HCO₃⁻, lowering the pH.
- Lower pH protonates certain residues (like histidine) in hemoglobin, stabilizing the T (tense) state, which has lower oxygen affinity.
- This promotes oxygen release in actively respiring tissues where CO₂ is high.
This physiological adaptation enhances oxygen delivery to where it’s most needed.
✘ Increases myoglobin’s oxygen affinity
Incorrect. The Bohr effect applies to hemoglobin, not myoglobin. Myoglobin’s oxygen affinity is not significantly affected by CO₂ or pH.
✘ Increases hemoglobin’s oxygen affinity
Incorrect. Increasing CO₂ concentration decreases hemoglobin’s oxygen affinity, promoting oxygen release — not retention.
✘ Decreases myoglobin’s oxygen affinity
Incorrect. Myoglobin does not exhibit the Bohr effect in the same way as hemoglobin, and its oxygen affinity is relatively stable.
✘ None of the answers are correct
Incorrect. One of the provided options is indeed correct (the effect on hemoglobin’s oxygen affinity).