[jonesito]

Hello. Just wondering I could get some clarification on this.

I know that for the blood, the most important buffer for acid-base balance is bicarbonate. I know that H2CO3 dissociates into H+ and HCO3-. When there is an increase in blood acidity, that increase in H+ attaches to HCO3- and is converted to H2O and CO2 and blown off by the lungs. That is the basis of the buffer system, to keep pH around 7.4. I'm not getting something though. When H2CO3 dissociates, you still have an acid and a base. If the base is used up by the increase in blood acidity, you still have the H+ that dissociated from HCO3- in the first place. This would keep the blood acidic.Does that make sense? It seems to counteract itself. If you use up the base with the new H+, then the H+ that dissociated from HCO3- in the first place is still there and you still have acidosis.

Any clarification would be great. Thanks!

[Borek]

If the base is used up by the increase in blood acidity, you still have the H+ that dissociated from HCO3- in the first place.

Base is used up to remove H⁺ no matter what its source is - so if base is used up, amount of H⁺ goes down.

[jonesito]

Thank you for the response. I still don't quite understand it, however. From what I understand, in order to produce a base, you have to produce an acid. When more acid is added, you still have the original acid that was produced to make the base. I'm basing this off of the H2O + CO2  H2CO3  H+ + HCO3-. Sorry, it's just not clicking. Thanks.

[Borek]

From what I understand, in order to produce a base, you have to produce an acid.

No, you consume the base when producing conjugate acid.

You start with blood with pH 7.4 - which means it contains 10^-7.4M H⁺. For some reason concentration of H⁺ goes up. Additional H⁺ reacts with HCO₃^-, CO₂ is blow out - and process continues till concentration of H⁺ gest back down to 10^-7.4M.