Under appropriate conditions, hemoglobin dissociates into its four subunits. Isolated α subunits bind oxygen, but the O2 saturation curve is hyperbolic instead of sigmoidal. In addition, its saturation curve is not affected by the presence of H+, CO2, or BPG. What do these observations indicate about the cooperativity and allosterism observed in hemoglobin?

Hemoglobin is an allosteric protein. An allosteric protein according to the MWC model, are those proteins that are characterized by molecules called oligomers and being formed by small equal subunits and allosteric proteins are chemically organized in such a way that they retain their symmetry.

In addition, these proteins can adopt several conformational states without losing symmetry.This leads us to the fact that hemoglobin being an allosteric protein also has the property called cooperativity. Cooperativity means that when PPO2 increases, the affinity of hemoglobin for oxygen increases. This is because when an oxygen molecule binds to hemoglobin, a signal is triggered that leads to other hemoglobin subunits increase their affinity to it as oxygen molecules bind together.