BMSC 200 Lecture Notes - Lecture 13: Myoglobin, Partial Pressure, Hemoglobin
12 Oct 2016
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A protein that binds o2 with high and constant affinity would saturate effectively with o2 in the lungs but not release it to tissues. A protein with a lower o2 affinity would be able to release o2 to tissues would tissues would not have sufficient affinity to saturate in the lungs. Hemoglobin solves the problems by undergoing a transition from a low affinity state to a high affinity state as more o2 molecules are bound. A single subunit protein with a single ligand binding site cannot achieve this effect because each molecule of ligand binds independently and cannot affect ligand binding of another molecule. If you imagine a situation where you have hemoglobin in solution but theres no oxygen around, its going to be in a state where each of the subunits is going to be in the t state.
