Why is the oxygen-hemoglobin dissociation curve sigmoid is shape?
Oxygen hemoglobin dissociation curve, is the curve relating percentage saturation of the oxygen carrying power of hemoglobin to the Po2. It has a characteristic sigmoid shape due to the T-R interconversion. In deoxyhemoglobin, globin units are tightly bound in a tense (T) configuration which reduces the affinity of the molecule for oxygen. When the first oxygen is bound, the bonds holding the globin units are released, producing a relaxed (R) configuration which exposes more oxygen binding sites. Thus, binding of one oxygen molecule increases the affinity of hemoglobin to bind other O2 molecules. Ref: Review of Medical Physiology, 22nd Edition By William F Ganong, Pages 667, 669; Textbook of Medical Physiology By Khurana, Page 440; Textbook of Physiology By Guyton and Hall, 10th Edition, Page 475
Binding of oxygen to hemoglobin reduces the affinity of Hb for Co2
Oxygen affinity of Hemoglobin decreases when the pH of blood falls
Binding of one oxygen molecule increases the affinity of binding of other O2 molecules
Binding of one oxygen molecule decrease the affinity of binding other O2 molecules HALDANE EFFECT