Acid-Base Balance

Question 1

What happens to HCO3 in the kidney?

Answer 1

Combines with H+ to produce CO2 and H2O which diffuse into cell in PCT. carbonic anhydrase acts on them again, producing H+ (recycled into urine) and HCO3 (released into blood)

Question 2

Identify and explain 3 complementary mechanisms of the kidney to increased acidity

Answer 2

1. Excretion of filtered H+
2. Filtered phosphate - hydrogen combines with phosphate to produce H2PO4 which is excreted
3. NH4 secretion - this is upregulated when there isnt enough PO4. Glutamine absorbed by PCT and broken down by glutaminase to produce NH4 and HCO3 - HCO3 enters blood and NH4 kidney where converted to NH3 as it is more stable. NH3 binds to H to be excreted as NH4

Question 3

Describe the differences between respiratory and metabolic acidosis

Answer 3

Respiratory - failure to ventilate away CO2 due to hypoventilation leads to increased pCO2 and compensatory increased HCO3

Metabolic - H+ addition due to lactic/ketoacid HCO3 decrease. May result in Kussmauls breathing due to respiratory drive to compensate

Question 4

Describe the differences between respiratory and metabolic alkalosis

Answer 4

Metabolic - H+ loss due to vomiting, diuretics, hyperaldosteronism, potassium depletion etc. Result sin volume depletion, chloride depletion and potassium depletion

Respiratory - Hyperventilation of CO2