Which statement is true about protons binding to hemoglobin?

• A. Protons stabilize the T-state increasing the affinity of hemoglobin for oxygen.
• B. Protons stabilize the T-state decreasing the affinity of hemoglobin for oxygen.
• C. Protons stabilize the R-state increasing the affinity of hemoglobin for oxygen.
• D. Protons stabilize the R-state decreasing the affinity of hemoglobin for oxygen.

Answer: (B)

Verified step by step guidance

1. Understand the structure of hemoglobin: Hemoglobin is a protein in red blood cells that carries oxygen. It can exist in two states: the T-state (tense) and the R-state (relaxed). The T-state has a lower affinity for oxygen, while the R-state has a higher affinity.
2. Learn about the Bohr effect: The Bohr effect describes how pH and carbon dioxide concentration affect hemoglobin's oxygen-binding affinity. An increase in protons (H+) or CO2 leads to a decrease in pH, which stabilizes the T-state of hemoglobin.
3. Analyze the role of protons: Protons bind to specific amino acid residues in hemoglobin, stabilizing the T-state. This stabilization decreases hemoglobin's affinity for oxygen, facilitating oxygen release in tissues where it is needed.
4. Evaluate the given statements: The correct statement should reflect the effect of protons on hemoglobin's state and oxygen affinity. Protons stabilize the T-state, which decreases the affinity of hemoglobin for oxygen.
5. Conclude with the correct statement: Based on the understanding of the Bohr effect and hemoglobin's states, the true statement is that protons stabilize the T-state, decreasing the affinity of hemoglobin for oxygen.