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Physiology

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Respiration

Question
5 out of 16
 

High affinity of HbF with O2 due to: (AIIMS MAY 2009)



A Decrease binding with 2,3 DPG

B Decrease concentration of Hb

C Increase in the Ph

D Bohr effect

Ans. A Decrease binding with 2,3 DPG

I. The affinity of fetal hemoglobin (hemoglobin F) for O2, which is greater than that for adult hemoglobin (hemoglobin A), facilitates the movement of O2 from the mother to the fetus.

II. The cause of this greater affinity is the poor binding of 2,3-BPG by the polypeptide chains that replace chains in fetal hemoglobin.

III. Some abnormal hemoglobins in adults have low P50 values, and the resulting high O2 affinity of the hemoglobin causes enough tissue hypoxia to stimulate increased red cell formation, with resulting polycythemia .

IV. It is interesting to speculate that these hemoglobins may not bind 2,3-BPG.

V. Factors affecting the concentration of 2,3-BPG in the red cells include

a. pHQ (acidosis inhibits red cell glycolysis, the 2,3-BPG concentration falls when the pH is low).

b. Thyroid hormones, growth hormone, and androgensQincrease the concentration of 2,3-BPG and the P50.

c. ExerciseQ has been reported to produce an increase in 2,3-BPG

d. Ascent to high altitudeQ triggers a substantial rise in 2,3-BPG concentration in red cells,

e. The affinity of fetal hemoglobin (hemoglobin F) for O2. The cause of this greater affinity is the poor binding of 2,3-BPG by the polypeptide chains that replace chains in fetal hemoglobinQ.

f. Red cell 2,3-BPG concentration is increased in anemiaQ and in a variety of diseases in which there is chronic hypoxia

g. In bank blood that is stored, the 2,3-BPG level falls. This decrease, is less if the blood is stored in citrate–phosphate–dextrose solutionQrather than the usual acid–citrate–dextrose solution.

h. Inosine increases 2,3 DPG in red blood cells. Q

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