Which of the following is/are effect of
increased 2,3-DPG on oxygen-
hemoglobin dissociation curve?
a) ↑ ed affinity of heamoglobin to oxygen
b) ↓ ed affinity of haemoglobin to oxygen
c) Left shift of oxygen-hemoglobin dissociation curve
d) Right shift of oxygen-hemoglobin dissociation curve
e) No change in oxygen-hemoglobin dissociation curve
Correct Answer - B:D
Ans. (B) ↓ ed affinity of haemoglobin to oxygen (D) Right shift
of oxygen-hemoglobin dissociation curve
[Ref: Ganong 25th/e p. 610-41; Guyton’s 12’h/e p.j56-57; A K lain
6’h/e p. 430]
- Oxygen-hemoglobin dissociation curve is 2,3 DPG in RBC.
- DPG is an optional by-product of the glycolytic pathway.
- DPG binds with deoxygenated hemoglobin but not with oxygenated
- Raised DPG concentration releases oxygen from oxyhemoglobin
by shifting the following reversible reaction to the right.
- One molecule of DPG binds with one mole of deoxyhemoglobin.
- Hence an increase in DPG concentration shifts the oxygen-
hemoglobin dissociation curve to the right.
- Thus 2,3 DPG causes delivery (unloading) of O, to the tissues.
- Fetal hemoglobin has considerably less affinity for 2,3 - DPG than
does adult hemoglobin therefore fetal hemoglobin has a greater
affinity for oxygen than adult hemoglobin.
In human blood, the affinity of fetal hemoglobin for 2,3-DPG is only
about 4O% that of adult hemoglobin.
This makes fetal hemoglobin behave as if 2,3-DPG levels are low