How does the bicarbonate buffer system work?

Abruzzi

New Member
I'm confused as to how the bicarbonate buffer system works. I know it's used to control pH levels of the blood.
I know that water and CO2 combine to form carbonic acid.
Carbonic acid then produces bicarbonate and H+ in a reversible reaction.
But, if pH increases shouldn't H+ be used to reduce alkalinity and not carbonic acid?

OnePunchBiopsy

Allergies: Clinic
7+ Year Member
HCO3- (aq) «------- H+ (aq) + CO32- (aq)

The pH is the concentration of protons (H+) in solution. As the concentration of protons increases, pH decreases.

Think of a buffer as a barrier that significantly decreases shifts in pH. Meaning, if you were to add a strong acid to pure water the pH would drop down very low (lets just say 1). However, if you added the same amount of strong acid to a buffered solution, the pH would not decrease as much (it could be 4 or 5 instead of 1).

This is because you add more acid, all the extra protons you are adding are being consumed by the CO32- , driving the reaction to the left to produce HCO3-, making the concentration of protons increase MUCH SLOWER than if the protons were floating around freely. This makes the pH drop slower, buffering it from dramatic changes.

Abruzzi

New Member
HCO3- (aq) «------- H+ (aq) + CO32- (aq)

The pH is the concentration of protons (H+) in solution. As the concentration of protons increases, pH decreases.

Think of a buffer as a barrier that significantly decreases shifts in pH. Meaning, if you were to add a strong acid to pure water the pH would drop down very low (lets just say 1). However, if you added the same amount of strong acid to a buffered solution, the pH would not decrease as much (it could be 4 or 5 instead of 1).

This is because you add more acid, all the extra protons you are adding are being consumed by the CO32- , driving the reaction to the left to produce HCO3-, making the concentration of protons increase MUCH SLOWER than if the protons were floating around freely. This makes the pH drop slower, buffering it from dramatic changes.
I see, so it's just resisting the acidic pH

Dr. Death

Full Member
5+ Year Member
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RogueBanana

ヽ（´ー｀）ノ
2+ Year Member
Look up LeChatelier's principle. I think that will clarify the situation.

The buffer system shields the solution's pH by taking the acidic protons and combining to form a neutral compound.
In this Case:
CO2 + H20 <-> H2CO2 <-> H+ + CO3-

How does this regulate blood pH? How does the body utilize this?

The system is linked closely to the respiratory system, which will increase or decrease respiration to decrease or increase CO2/H2O concentration. According to Lechatelier's principle, this will shift the equillibrium to increase pH (less H+ floating around) or decrease pH (More H+ Floating around)

For example, we have a child with diabetic ketoacidosis, so he has an extremely high H+ concentration in his blood. His body isn't stupid, and will act to correct the deficiency as best it can. SO the child will most likely present to the ED hyperventilating. Why? look at the equation:

If we remove CO2, equillibrium will shift to the left, forcing H+ and CO3- to bond, making more H2CO2, which dissociates into CO2 & H2O which the lungs blow off. The effect of this is to increase blood pH, (get rid of the acid). Hyperventillation is an indication that there is too much acid to handle, and the body is fighting as hard as it can to get blood pH to survivable levels.

CO2 + H20 <-> H2CO2 <-> H+ + CO3-

Blown off<-------------------------Recombines in blood

hope this helps