Physiology The oxygen hemoglobin dissociation curve is sigmoid because A Binding of one oxygen molecule increases the affinity of binding other O2 molecules B Binding of one oxygen molecule decrease the affinity of binding other O2 molecules C Oxygen affinity of Hemoglobin decreases when the pH of blood falls D Binding of oxygen to hemoglobin reduces the affinity of Hb for CO2 💡 Explanation The oxygen hemoglobin dissociation curve is sigmoid because ✓ Correct Answer: A. Binding of one oxygen molecule increases the affinity of binding other O2 molecules