For each of the following, indicate whether an increase in the concentration of that substance will increase, decrease or have no substantial effect on the binding affinity for oxygen to the protein hemoglobin (circle one answer in each category).
Substance Effect on Oxygen Binding Affinity
H3O^+ Increase Decrease No effect
Cr Increase Decrease No effect
CO Increase Decrease No effect
BPG^* Increase Decrease No effect
*BPG = 2,3-Bisphosphoglycerate

In the given question all the four substances individual increase in concentration will decrease the binding affinity for oxygen to the protein hemoglobin

H3O+ acts as an acid which means its pH will be less and as pH will be less there will be more hydrogen ions,higher will be the level of carbon dioxide and therefore affinity of hemoglobin will be less or we can as H3O+ concentration will increase binding affinity for oxygen to hemoglobin will decrease
Cr(Chromium) rapidly binds to the hemoglobin hence decreases the binding affinity of oxygen to hemoglobin
CO(Carbon monoxide) has the same binding site as oxygen and hence binds with hemoglobin and forms carboxyhemoglobin therefore oxygen is not able to bind to hemoglobin and its binding affinity decreases
BPG is an acidic molecule and present in relatively higher concentration in red blood cells(RBCs);at higher altitude BPG concentration increases in RBCs that facilitate dissociation of oxygen from hemoglobin and hence decreases its affinity