Physiology The sigmoid nature of Hb-O2 dissociation curve is because of: A Binding of one O2 molecule increase the affinity for the next O2 molecule. B Alpha chain has more affinity for O2 than beta chain C Beta chain has more affinity for than alpha chain D Hemoglobin in acidic in nature. 💡 Explanation The sigmoid nature of Hb-O2 dissociation curve is because of: ✓ Correct Answer: A. Binding of one O2 molecule increase the affinity for the next O2 molecule.