Sigmoidal binding curves hemoglobin

We can determine quantitatively the physiological significance of the sigmoid nature of the hemoglobin oxygen-binding curve, or, in other words, the biological importance of cooperativity. The equation... 

Hemoglobin (Hb) behaves differently. Its sigmoidal binding curve can be fitted by an association-constant expression with a greater-than-first-power dependence on the oxygen concentration ... 

The sigmoidal binding curve displayed by many allosteric enzymes resembles the curve for the cooperative binding of 02 to hemoglobin. 

The 02-binding curve for myoglobin is hyperbolic, but for hemoglobin it is sigmoidal, a consequence of cooperative interactions in the tetramer. Cooperativ-ity maximizes the ability of hemoglobin both to load O2 at the PO2 of the lungs and to deliver O2 at the PO2 of the tissues. 

Thus, for hemoglobin (Hb) the oxygen binding curves are sigmoidal as is shown in the above figure. The fact that n exceeds the unit can be ascribed physically to the fact that attachment of O2 to one heme group... 

Hemoglobin has been a favorite protein molecule for designing and testing various models of the molecular basis of subunit interactions in multisubunit proteins. In the 1960s, two mechanisms were advanced to account for the sigmoidal nature of the oxygen binding curve for Hb A, one proposed by Monod et al. (1965) based on a... 

Answer These observations indicate that the cooperative behavior—the sigmoid 02-binding curve and the positive cooperativity in ligand binding—of hemoglobin arises from interaction between subunits. 

Heme (7 ) with poly(L-lysine) is slowly oxidized at pH 12 to the oxygenated complex sigmoid curve of O2 adsorption like In hemoglobin also binds CO and CN"... 

Figure 7.12 T-to-R transition. The observed binding curve for hemoglobin can be seen as a combination of the binding curves that would be observed if all molecules remained in the T state or if a l of the molecules were in the R state. The sigmoidal curve is observed because molecules convert from the T state into the R state as oxygen molecules bind.

---