Hemoglobin (Hb) can be viewed as having two quaternary states, a low oxygen affi

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?

1) Upon binding a molecule of oxygen, Hb undergoes a conformational change that makes the binding of subsequent O2 molecules easier.
2) 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.
3) 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.
4) Site-directed mutagenesis studies in which the proximal His residues of the F helix have been replaced by glycines have indicated the mutant protein still shows cooperativity of O2 binding.

Explanation / Answer

A1) Upon binding a molecule of oxygen, Hb undergoes a conformational change that makes the binding of subsequent O2 molecules easier.

The haemoglobin bind to second and third molecule oxygen to Hb as compare to first oxygen molecule leading to change of confirmation as oxygen bind. The fourth oxygen molecule is more difficult to bind. The binding of oxygen to haemoglobin graph is sigmoidal graph

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