Role of H+ and CO2 in Hb-O2 affinity

[shefv]

I know that both H+ and CO2 compete with O2 for the binding spot on Hb.

Using the blood buffer equation:

H2O + CO2 -> H2CO3 -> HCO3- + H+

So I came across a concept/question that stated: Increasing HCO3- would get rid of H+ and increase affinity of Hb for O2. But wouldn't that also contribute to an increase in CO2 which decreases the affinity of Hb for O2? I am confused as to why they are not taking he affects of CO2 into consideration.

How should I approach this questions? I immediately thought of the blood buffer equation and thought that more HCO3- would result in more CO2 being produced which would decrease affinity of Hb for O2. What am I doing wrong?

How would an increase in bicarbonate (HCO_3^-HCO3−) relative to all other molecules in the blood affect the oxygen affinity of hemoglobin and why?
Please choose from one of the following options.

• Decrease oxygen affinity by directly binding with hemoglobin
• Increase oxygen affinity by binding with free protons
• Decrease oxygen affinity by binding with free protons
• Increase oxygen affinity by directly binding with hemoglobin

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[Quinoline]

Increased HCO3- decreases H+
H+ stabilizes deoxy/reduced form of Hb
So the oxygenated state of Hb is more favored with increased H+

Increased HCO3- also increases CO2
CO2 also binds more to deoxy/reduced form of Hb, but not at the same place as O2

While CO2 and H+ both bind more on deoxy Hb, I think the difference between H+ and CO2 is that H+ stabilizes the deoxy form of Hb, while CO2 does not have the same stabilizing effect. So the increased CO2 doesn't affect O2 affinity.

 

[691622]

Look up Bohr effect