If identical samples of human blood are treated with different concentrations of
ID: 277542 • Letter: I
Question
If identical samples of human blood are treated with different concentrations of chloride ions, the sample with the higher [CI] will be found to have a higher concentration of free oxygen in solution (that is, oxygen NOT bound to hemoglobin). Based on this information, would you expect chloride ions to stabilize the T state or R state of hemoglobin? High concentrations of 2,3-BPG and carbon monoxide both inhibit the oxygen-carrying capacity of hemoglobin. The animation illustrates how 2,3-BPG binds at the interface of two ? subunits and stabilizes the T state of hemoglobin. Carbon monoxide, on the other hand (as discussed in section 6.2 of the text), binds to the heme iron in the same manner as oxygen. Would you expect carbon monoxide binding to shift the conformational equilibrium in favor of the T state or the R state?Explanation / Answer
In T-state, hemoglobin has lower affinity to the oxygen, meaning the oxygen will not be bound to the hemoglobin. In R-state, hemoglobin has higher affinity to oxygen, meaning the oxygen will be bound to the hemoglobin. The question states that higher [Cl-] concentration leads to higher free oxygen, that is higher unbound oxygen. This occurs only if the hemoglobin is in T-state. So [Cl-] ions stabilize the T-state of hemoglobin.
Carbon monoxide increases the affinity of hemoglobin towards oxygen (same as oxygen), that is the binding of carbon monoxide leads to bound oxygen that is not released into the tissues. Thus, carbon monoxide shifts the conformational equlibrium in favor of R-state.
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