acid base mini learning

Question 1

What is seen in metabolic acidosis ?

Answer 1

low bicarbonate

Question 2

What is seen in metabolic alkalosis ?

Answer 2

high bicarbonate

Question 3

What is seen in respiratory acidosis ?

Answer 3

high CO2

Question 4

What is seen in respiratory alkalosis ?

Answer 4

low CO2

Question 5

What is the formula involving CO2 and bicarbonate ?

Answer 5

CO2 + H2O => H+ + HCO3-

Question 6

What class of enzyme converts CO2 + H2O into H+ and bicarbonate in the kidney ?

Answer 6

CARBONIC ANHYDRASE
- CA2 (intracellular)
- CA4 (extracellular, in the nephron lumen)

Question 7

How does bicarbonate get from nephron lumen to blood stream ?

Answer 7

• 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

Question 8

Which carbonic anhydrase is intracellular in the kidney ?

Answer 8

CA 2

Question 9

Which carbonic anhydrase is extracellular in the kidney ?

Answer 9

CA 4

Question 10

What do carbonic anhydrases do ?

Answer 10

catalyse the reaction:

CO2 + H2O <=> H + HCO3-

Question 11

where is 80% of bicarbonate reabsorbed in the kidney ?

Answer 11

PCT

Question 12

Where are small amounts of bicarbonate reabsorbed in the kidney ?

Answer 12

• Thick ascending limb (loop of henle)
• DCT
• Collecting ducts

Question 13

what % of bicarbonate is reabsorbed in the thick ascending limb of the loop of henle ?

Answer 13

10%

Question 14

what % of bicarbonate is reabsorbed in the DCT ?

Answer 14

6%

Question 15

what % of bicarbonate is reabsorbed in the collecting ducts ?

Answer 15

4%

Question 16

roughly how much bicarbonate is excreted via the kidneys ?

Answer 16

< 0.01%

Question 17

Where is the majority of ammonium (NO4+) secreted into in the kidney ?

Answer 17

PCT

Question 18

In which section of the kidney is ammonium recycled ?

Answer 18

the medulla (loop of henle)

Question 19

Where is the majority of H+ secreted as titratable acids in the kidney ?

Answer 19

PCT

some in the DCT and collecting ducts

Question 20

How much ammonium is excreted from the kidney each day ?

Answer 20

~ 40 mmol

Question 21

How much H+ is excreted as titratable acids from the kidney each day ?

Answer 21

~ 30 mmol

Question 22

How much acid does the kidney need to secrete per day in order to maintain pH balance ?

Answer 22

70 mmol acid

(40mmol NH4+ and 30mmol titratable acid)

Question 23

Is bicarbonate usually
a) secreted into the kidney ?
b) excreted from the kidney ?
c) reabsorbed by the kidney ?

Answer 23

all bicarbonate is reabsorbed

Question 24

What are the 2 forms H+ is excreted from the body in ?

Answer 24

• Ammonium (NH4+)
• Titratable acids

Question 25

What processes maintain the excretion of H+ and absorption of HCO3- in the kidney?

Answer 25

• basolateral HCO3- exit
• apical H+ secretion

dependent on carbonic anhydrase enzymes 2 and 4

Question 26

What are the 4 types of renal tubule acidosis ?

Answer 26

1 = DCT
2 = PCT
3 = combo of PCT and DCT
4 = hyperkalaemia (hypoaldosteronism)

Question 27

What causes renal tubule acidosis (RTA)?

Answer 27

defects in HCO3- reabsorption and H+ secretion = acid-base imbalance/defects