PCO2 level due to cholera toxin

[UIUCstudent]

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Cholera toxin causes diarrhea which leads to loss of sodium bicarbonate. The loss of bicarbonate ion leads to metabolic acidosis. Le chatelier's principle goes into effect and CO2 +H2O is converted into H2CO3 and invariably dissociates into H+ and HCO3- ions. So how come BR says PCO2 levels increases. It seems like it should decrease instead due to le Chatelier.

p168 of BR bio book 1

 

[soby10]

H20+Co2 <----> H2Co3<------>H + HCo3-

So if H+ increases bc of a low PH LeChatlier will shift to left to cause a Co2 increase. To offset the H+ increase

 

[UIUCstudent]

H20+Co2 <----> H2Co3<------>H + HCo3-

So if H+ increases bc of a low PH LeChatlier will shift to left to cause a Co2 increase. To offset the H+ increase

but then if you do that then there won't be enough HCO3- ? The body wants to restore the loss of HCO3- due to the cholera toxin.

 

[soby10]

In acidosis the body doesn't want to restore Hco3- the body wants to restore physiological PH. Think of the loss of base meaning a increase in acid. So if there is a disturbance it will be restored via blood buffering equation H20+co2<-----> H2Co3<----->H+ +Hco3-
Therefore increasing H+ ion disturbs equilibrium, at this point blood is acidic a shift to the left will cause more Co2, increasing the basicity of blood. PH is shifted back to a physiological PH of 7.4. At this point blood is back in balance, remember this is a equilibrium equation meaning that every species is being made forwards and backwards in the equation so HCo3- will also eventually be made.