The Sigmoid (S-Shaped) Binding Curve That Describes the Interaction of O₂

Multiple Choice

The sigmoid (S-shaped) binding curve that describes the interaction of O₂ with hemoglobin is a direct consequence of

A) allosteric regulation by 2,3-bisphosphoglycerate.
B) cooperativity among subunits.
C) covalent bonds between alpha beta?heterodimers.
D) orientation of histidine residues near the heme groups.
E) reversible oxidation and reduction of heme iron atoms.