2,3 BPG and lung oxygen saturation

[deleted783484]

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Hi! I had two questions:
1- 2,3 BPG allosterically binds to Hemoglobin changing it to its T state so it has lower affinity for oxygen.

I am confused on how the percent saturation of oxygen in the lungs is still able to reach 100% if Hb cannot bind to oxygen as readily?

2- Since fetal hemoglobin has a higher affinity to oxygen and it has low affinity for 2,3BPG how is it able to release oxygen to the tissues if it has such a high affinity for oxygen?

Thank you

 

[Neuroplasticity]

2- Since fetal hemoglobin has a higher affinity to oxygen and it has low affinity for 2,3BPG how is it able to release oxygen to the tissues if it has such a high affinity for oxygen?

In tissues, the partial pressure of oxygen is lower and CO2 is higher (bohr effect), causing release of oxygen.

 

[CoomassieBlue57]

Hi! I had two questions:
1- 2,3 BPG allosterically binds to Hemoglobin changing it to its T state so it has lower affinity for oxygen.

I am confused on how the percent saturation of oxygen in the lungs is still able to reach 100% if Hb cannot bind to oxygen as readily?

2,3 DPG shifts the curve in the x-axis. On the MCAT assume the saturation level is still able to reach 100%. pO2 in ambient air is around 160 mmHg, while in the alveoli pO2 is about 100 mmHg. Even with the right shift, pO2 will still reach 100% saturation up to a certain point on the sigmoid curve.