Acid/Base Overview

Question 1

Acid/Base Equation

Answer 1

CO2 + H2O <> H2CO3 <> HCO3(-) + H(+)

Question 2

Which enzyme converts carbon dioxide [CO2] to carbonic acid [H2CO3]?

Answer 2

Carbonic anhydrase

-expressed in the renal tubules
-also in red blood cells

Question 3

What would be the effect of increasing CO2 on H(+) and pH?

Answer 3

-shift to the product side -> increase in H(+)

-pH = -log [H+] -> if H(+) goes up, pH goes down

Question 4

What would be the effect of increasing HCO3(-) on H(+) and pH?

Answer 4

Equation:
CO2 + H2O <> H2CO3 <> HCO3(-) + H(+)

if HCO3(-) increases it will more likely combine with H(+) and form H2CO3

-pH = log [H+] -> H(+) goes down, pH goes up

Question 5

How does respiration affect CO2 concentration?

Answer 5

Breathing fast: decrease in CO2

Breathing slow: increase in CO2

Question 6

How does the kidney regulate bicarbonate [HCO3(-)]?

[A]

Answer 6

In the tubular epithelial cells:
H2O + CO2 -> H2CO3 (via carbonic anhydrase) ->
H(+) + HCO3(-)

H(+) goes into the tubule (urine)
HCO3(-) goes into the interstitial fluid (blood)

in the tubular lumen H(+) combines with HCO3(-) to H2CO3 -> H2O + CO2

-considered reabsorbtion because in the tubules we loose on HCO3(-) and another (different) HCO3(-) goes into the interstitial fluid

Question 7

How does the kidney regulate bicarbonate [HCO3(-)]?

[B]

Answer 7

In the tubular epithelial cells:
H2O + CO2 -> H2CO3 (via carbonic anhydrase) ->
H(+) + HCO3(-)

H(+) goes into the tubule (urine)
HCO3(-) goes into the interstitial fluid (blood)

in the tubular lumen H(+) combines with HPO4(-2) to H2PO4(-)

-NO Reabsorption

Question 8

How does the kidney regulate bicarbonate [HCO3(-)]?

[C]

Answer 8

Reabsorption of Glutamine -> into tubular epithelia cells -> Glutamine degrades into NH4(+) and HCO3(-)

NH4(+) is secreted back into the tubular lumen and will be excreted

HCO3(-) will move into the interstitial fluid (blood)

Question 9

How does an increase in HCO3(-) affect pH?

Answer 9

pH = -log [H+]

HCO3(-) will decrease H+ because the reaction will be driven away from H(+) to H2CO(-), so pH goes up

Question 10

How does the kidney react if the pH is high and there is a lot of HCO3(-)?

Answer 10

The kidney will turn off the 3 ways of HCO3(-) production