Hemoglobin is a tetrameric protein consisting of two α and two βpolypeptide subunits. The structure of the α and β subunits are remarkably similar to that of myoglobin. However, at a number of positions, hydrophilic residues in myoglobin have been replaced by hydrophobic groups in hemoglobin.

a) How can this observation be reconciled with the generalization that hydrophobic residues fold into the interior of proteins?

b) In this regard, what can you say about the nature of the interaction that determine the quaternary structure of hemoglobin?

c) How this tetrameric association make the hemoglobin good for oxygen transport? What effects promote the release of oxygen where it is needed?