Factors affecting the affinity of hemoglobin for oxygen are all of the following, EXCEPT:
Correct Answer: PCO2
Description: Three impoant conditions affect the oxygen hemoglobin dissociation curve: pH, the temperature, and the concentration of 2,3-diphosphoglycerate (2,3-DPG). The decrease in O2 affinity of hemoglobin when pH of blood falls is called the Bohr effect and is closely related to the fact that deoxyhemoglobin binds H+ more actively than does oxyhemoglobin. The pH of blood falls as its CO2 content increases, so that when the PCO2 rises. But CO2 does not change directly the affinity of hemoglobin for oxygen. The greater affinity of fetal hemoglobin F than adult hemoglobin A for O2 facilitates the movement of O2 from the mother to the fetus. The cause of this greater affinity is the poor binding of 2,3-DPG by the g polypeptide chains that replace b chain in fetal hemoglobin. Some abnormal hemoglobins have high O2 affinity causes enough tissue hypoxia to stimulate increased red cell formation, with resulting polycythemia. Ref: Medical Physiology: Principles for Clinical Medicine, 4th Ed, page 350
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