20. Dissociation Curves of Hemoglobin Hydrogen ions affect the conformation of hemoglobin—a drop in pH shifts the oxygen dissociation curve toward the right. At a given PO2, hemoglobin gives up more O2 at pH 7.2 than at pH 7.4 , the normal pH of human blood. The pH decreases in very active tissues because the CO2 produced by respiration reacts with water, forming carbonic acid. Hemoglobin then releases more O2 , which supports the increased cellular respiration in the active tissues.
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