1. Below are two figures showing the binding site of O2 on hemoglobin and the plot of the binding behavior of O2 for hemoglobin. Hemoglobin can also bind the allosteric modifier bisphosphoglycerate (BPG) at a different location and change its conformation upon binding. This conformational change is also reflected in the shape change of the sigmoidal binding curve. Iron atom O2 loaded in lungs O2 unloaded in tissues Heme group Polypeptide chain Tissues Lungs 1.0 0.8 0.6 0.4 0.2 Y 20 40 60 80 100 pO2 (torr) a. At increased levels of BPG, which direction would you expect the binding curves of oxygen to shift? b. How does BPG affect the total amount of O2 that can bind? c. How does BPG affect the affinity of O2 binding to hemoglobin? d. Does BPG increase or decrease the KD of oxygen binding? e. Would you expect the BPG levels of someone living at high altitudes to be higher or lower?
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At increased levels of BPG, the binding curves of oxygen would shift to the right. This is because BPG binding to hemoglobin decreases its affinity for oxygen, making it more difficult for oxygen to bind. Show moreā¦
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Shaiju T.
Information Bisphosphoglycerate (BPG) is an allosteric modifier that binds to the central cavity of hemoglobin. BPG affects hemoglobin affinity for oxygen by binding at a site different than the oxygen binding site and promoting a shape change in the molecule. The result of BPG binding is that oxygen binding curves shift right. When the small molecule is the same as the normal ligand for the protein this interaction is called homotropic as it is for oxygen and hemoglobin. The interaction of BPG with hemoglobin is heterotropic since BPG and oxygen are not the same and do not bind to the same site. 24. The molecule BPG binds to the deoxy form of hemoglobin in the central cavity. Explain why that makes sense for oxygen delivery and why BPG is said to stabilize the deoxy state. 25. How do the levels of O2 in the atmosphere compare at sea level versus high altitude? Predict the blood levels of BPG for people who live at high altitudes, like Denver. How will those levels of BPG help their hemoglobin function better?
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