BIO 361 Lecture Notes - Lecture 15: Asparagine, Stereochemistry, John Wiley & Sons
10 Jul 2016
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Document Summary
Bohr effect is a description of the affinity of hemoglobin for oxygen being lowered as ph is lowered. The value of p50 is increased as the ph is decreased. Oxyhemoglobin (oxygen-bound hemoglobin) is a stronger acid than deoxyhemoglobin (oxygen- dissociated hemoglobin). Oxyhemoglobin gives up protons as it binds oxygen (acidic character) Binding of oxygen is associated with a small change in the diameter of the heme iron. There is also a change in the relationship between the heme iron and its third ligand called heme-linked histidine. There is a histidine holding an iron in each of the four polypeptide chains and is the 8th residue on the 6th helix of each polypeptide chain. When oxygen binds to the hemoglobin molecule, there is a steric problem that develops between the heme-linked histidine and the tetrapyrrole ring. That can be corrected only altering the tilt of the heme-linked histidine with respect to the plane of the tetrapyrrole ring.
