Question

Hemoglobin (Hb) can be viewed as having two quaternary states, a low oxygen affinity state (T), and a high oxygen affinity state (R). Which of the following statements about the binding of O2 by Hb are true? Upon binding a molecule of oxygen, Hb undergoes a conformational change that makes the binding of subsequent O2 molecules more favored. The conformational change induced in Hb upon binding oxygen is the result of a small movement (0.2 Å) of the iron cation into the center of heme. Site-directed mutagenesis studies have indicated that the cooperativity of O2 binding in Hb is attributable to the movement of the F helix in Hb. Site-directed mutagenesis studies in which the proximal His residues of the F helix have been replaced by glycines have indicated the mutant protein still shows cooperativity of O2 binding.

Answer 1

Answer;

The statements that are True are;

• Upon binding a molecule of oxygen, Hb undergoes a conformational change that makes the binding of subsequent O2 molecules easier.
• The conformational change induced in Hb upon binding oxygen is the result of a small movement (0.2 Å) of the iron cation in the center of heme.
• Site-directed mutagenesis studies have indicated that the cooperativity of O2 binding in Hb is attributable to the movement of the F helix in Hb.

Explanation;

• Hemoglobin is a key pigment in the blood that transports oxygen gas to all the tissues in the body. It is made up of two types of chains; that is two alpha chains and two beta chains.  
• in its deoxygenated state hemoglobin has a low affinity for oxygen compared to myoglobin. When oxygen is bound to the first subunit of hemoglobin it leads to subtle changes to the quaternary structure of the protein. This in turn makes it easier for a subsequent molecule of oxygen to bind to the next subunit.