2, 3-BPG

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.

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