What does cooperative binding mean? Explain this in the context of hemoglobin. (4p)
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Answer
Cooperative binding means that the binding of an oxygen to hemoglobin makes it more likely for the molecule to bind more oxygen.
This is because when an oxygen binds to hemoglobin the structure becomes less tense as one αβ-dimer rotates 15 degrees, which increases its affinity for oxygen at other binding sites.
Release of an oxygen promotes also further release.
Due to the cooperativity hemoglobin has a sigmoidal binding curve at different partial pressures of oxygen.
Cooperativity enables hemoglobin to be a good oxygen transporter.