In the lungs, the _________ pressure of CO₂ causes hemoglobin to _________ CO₂ and H⁺. The _________ pressure of O₂ causes O₂ to _________ hemoglobin, allowing for its transportation to the tissues.

• A. Low; Bind; Low; Release.
• B. High; Bind; Low; Release.
• C. High; Bind; High; Release.
• D. Low; Release; High; Bind.
• E. High; Release; Low; Bind.
• F. Low; Release; Low; Bind. Blood pH in Tissues ≈ 7.2 Blood pH in Lungs ≈ 7.6 Blood pH ≈ 7.4

Answer: (D)

Verified step by step guidance

1. Understand the role of hemoglobin in gas exchange: Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to the tissues and helps transport carbon dioxide back to the lungs.
2. Consider the effect of partial pressures: In the lungs, the partial pressure of oxygen is high, which promotes the binding of oxygen to hemoglobin. Conversely, the partial pressure of carbon dioxide is low, which facilitates the release of CO2 and H+ from hemoglobin.
3. Analyze the Bohr effect: The Bohr effect describes how changes in blood pH and CO2 concentration affect hemoglobin's affinity for oxygen. In the lungs, a higher pH (around 7.6) increases hemoglobin's affinity for oxygen, promoting oxygen binding.
4. Apply the concept to the given options: The correct sequence involves low CO2 pressure leading to the release of CO2 and H+, and high O2 pressure leading to the binding of O2 to hemoglobin.
5. Relate blood pH to hemoglobin function: In tissues, the blood pH is lower (around 7.2), which facilitates the release of oxygen from hemoglobin due to the Bohr effect, while in the lungs, the higher pH (around 7.6) enhances oxygen binding.