Which of the following factors is responsible for decreasing hemoglobin's affinity for oxygen, as described by the Bohr effect?
Solution
Correct Answer: Option B
- The Bohr effect describes how certain physiological conditions influence hemoglobin's affinity for oxygen.
- Specifically, elevated levels of carbon dioxide (CO₂) and hydrogen ions (H⁺) in the blood lead to a decrease in hemoglobin’s oxygen affinity.
- This is because these factors promote the release of oxygen from hemoglobin, facilitating oxygen delivery to metabolically active tissues.
- When CO₂ levels rise, more hydrogen ions are produced through the reaction catalyzed by carbonic anhydrase, resulting in a lower pH (more acidic environment).
- This acidic environment causes a conformational change in hemoglobin, stabilizing the tense (T) state of hemoglobin that has a lower affinity for oxygen.
- Consequently, oxygen is more readily released where it is needed most.
- Conversely, factors such as increased partial pressure of oxygen (pO₂), decreased body temperature, and low levels of 2,3-bisphosphoglycerate (2,3-BPG) tend to increase hemoglobin’s affinity for oxygen, which is the opposite effect of the Bohr effect.
- In summary, the key point is that the Bohr effect is driven by elevated CO₂ and H⁺ levels, which reduce hemoglobin’s oxygen affinity, enhancing oxygen delivery under conditions where tissues require more oxygen.
Reference: Guyton and Hall Textbook of Medical Physiology, Volume 1, Chapter 43: Oxygen Transport
- Specifically, elevated levels of carbon dioxide (CO₂) and hydrogen ions (H⁺) in the blood lead to a decrease in hemoglobin’s oxygen affinity.
- This is because these factors promote the release of oxygen from hemoglobin, facilitating oxygen delivery to metabolically active tissues.
- When CO₂ levels rise, more hydrogen ions are produced through the reaction catalyzed by carbonic anhydrase, resulting in a lower pH (more acidic environment).
- This acidic environment causes a conformational change in hemoglobin, stabilizing the tense (T) state of hemoglobin that has a lower affinity for oxygen.
- Consequently, oxygen is more readily released where it is needed most.
- Conversely, factors such as increased partial pressure of oxygen (pO₂), decreased body temperature, and low levels of 2,3-bisphosphoglycerate (2,3-BPG) tend to increase hemoglobin’s affinity for oxygen, which is the opposite effect of the Bohr effect.
- In summary, the key point is that the Bohr effect is driven by elevated CO₂ and H⁺ levels, which reduce hemoglobin’s oxygen affinity, enhancing oxygen delivery under conditions where tissues require more oxygen.
Reference: Guyton and Hall Textbook of Medical Physiology, Volume 1, Chapter 43: Oxygen Transport
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