2,3-Bisphosphoglycerate (2,3-BPG) is a molecule found in red blood cells that plays a crucial role in regulating oxygen binding and release by hemoglobin.
Role of 2,3-BPG :-
1. Binding to hemoglobin: 2,3-BPG binds to the beta chains of deoxygenated hemoglobin (deoxyhemoglobin) in the central cavity between the two beta subunits. This binding stabilizes the T (tense) state of hemoglobin.
2. Decreasing oxygen affinity: By stabilizing the T state, 2,3-BPG reduces hemoglobin’s affinity for oxygen. This means that in the presence of 2,3-BPG, hemoglobin is more likely to release oxygen to the tissues.
Shift direction | Factor | Effect on oxygen affinity | Physiological implications |
Right shift | 1. Increased CO₂ (Hypercapnia) 2. Increased H⁺ (Decreased pH, acidosis) 3. Increased temperature 4. Increased 2,3-BPG 5. Exercise | Decreased oxygen affinity | Enhanced oxygen delivery to tissues |
Left shift | 1. Decreased CO₂ (Hypocapnia) 2. Decreased H⁺ (Increased pH, alkalosis) 3. Decreased temperature 4. Decreased 2,3-BPG 5. Presence of fetal hemoglobin (HbF) | Increased oxygen affinity | Reduced oxygen delivery to tissues |
Oxygen Affinity :-
1. High affinity state (R state): In the lungs, where the oxygen concentration is high, hemoglobin binds oxygen tightly, favoring the R (relaxed) state.
2. Low affinity state (T state): In the tissues, where oxygen concentration is lower, hemoglobin releases oxygen more readily, favoring the T state. 2,3-BPG facilitates this release by binding to hemoglobin and promoting the T state.
Physiological Importance: This regulation ensures efficient oxygen uptake in the lungs and delivery to the tissues. Without 2,3-BPG, hemoglobin would hold onto oxygen too tightly, impairing oxygen delivery.