acid base mini learning Flashcards
What is seen in metabolic acidosis ?
low bicarbonate
What is seen in metabolic alkalosis ?
high bicarbonate
What is seen in respiratory acidosis ?
high CO2
What is seen in respiratory alkalosis ?
low CO2
What is the formula involving CO2 and bicarbonate ?
CO2 + H2O => H+ + HCO3-
What class of enzyme converts CO2 + H2O into H+ and bicarbonate in the kidney ?
CARBONIC ANHYDRASE
- CA2 (intracellular)
- CA4 (extracellular, in the nephron lumen)
How does bicarbonate get from nephron lumen to blood stream ?
- H+ combines with bicarbonate via CA4 in the lumen
- creates CO2 and H2O
- CO2 diffuses into cell
- CO2 combines with water inside cell via CA2
- forms H+ (released out of cell to restart process) and bicarbonate
- bicarbonate transferred out via transport protein in basolateral membrane
Which carbonic anhydrase is intracellular in the kidney ?
CA 2
Which carbonic anhydrase is extracellular in the kidney ?
CA 4
What do carbonic anhydrases do ?
catalyse the reaction:
CO2 + H2O <=> H + HCO3-
where is 80% of bicarbonate reabsorbed in the kidney ?
PCT
Where are small amounts of bicarbonate reabsorbed in the kidney ?
- Thick ascending limb (loop of henle)
- DCT
- Collecting ducts
what % of bicarbonate is reabsorbed in the thick ascending limb of the loop of henle ?
10%
what % of bicarbonate is reabsorbed in the DCT ?
6%
what % of bicarbonate is reabsorbed in the collecting ducts ?
4%
roughly how much bicarbonate is excreted via the kidneys ?
< 0.01%
Where is the majority of ammonium (NO4+) secreted into in the kidney ?
PCT
In which section of the kidney is ammonium recycled ?
the medulla (loop of henle)
Where is the majority of H+ secreted as titratable acids in the kidney ?
PCT
some in the DCT and collecting ducts
How much ammonium is excreted from the kidney each day ?
~ 40 mmol
How much H+ is excreted as titratable acids from the kidney each day ?
~ 30 mmol
How much acid does the kidney need to secrete per day in order to maintain pH balance ?
70 mmol acid
(40mmol NH4+ and 30mmol titratable acid)
Is bicarbonate usually
a) secreted into the kidney ?
b) excreted from the kidney ?
c) reabsorbed by the kidney ?
all bicarbonate is reabsorbed
What are the 2 forms H+ is excreted from the body in ?
- Ammonium (NH4+)
- Titratable acids
What processes maintain the excretion of H+ and absorption of HCO3- in the kidney?
- basolateral HCO3- exit
- apical H+ secretion
dependent on carbonic anhydrase enzymes 2 and 4
What are the 4 types of renal tubule acidosis ?
1 = DCT
2 = PCT
3 = combo of PCT and DCT
4 = hyperkalaemia (hypoaldosteronism)
What causes renal tubule acidosis (RTA)?
defects in HCO3- reabsorption and H+ secretion = acid-base imbalance/defects
