Acid Base Balance Flashcards
Define pH
pH = -log10[H+]
How is pH buffered in the circulation?
H+ + HCO3-
to H2CO3
to H2O + CO2
What is the Henderson-Hasselbach equation?
pH = pK + log10 [base]/[acid]
What is the Henderson Hasselbach equation in relation to HCO3-?
pH = pK + log10[HCO3-]/0.22xPco2
Where Pco2 is the partial pressure of CO2
When is H+ produced?
ATP hydrolysis
During anaerobic respiration with the production of lactate
During the production of ketones
During ingestion of acids
How is HCO3- absorbed in the proximal tubule?
Carbonic anhydrase in the filtrate converts it to water and CO2
Carbonic anhydrase then converts it back to HCO3-
How is HCO3- excreted from the proximal tubule?
Via Na+ cotransporters
What is reabsorption of HCO3- dependent on?
Na+/H+ exchanger to maintain H+ concentration in the tubule
What promotes de novo HCO3- production?
CO2 from the vasa recta
How much HCO3- is reabsorbed?
At rest, almost all
An excess will not be reabsorbed
Where is H+ secreted in the nephron?
In the distal tubule
How is H+ secreted in the distal tubule?
H+K+ATPase
H+ATPase
How is free concentration of H+ in urine kept low?
Phosphate buffer
H+ HPO42- to H2PO4-
Where is ammonia secreted in the nephron?
Ammonium ion is produced in the proximal tubule by conversion of glutamine to glutamic acid and alpha ketoglutarate
NH4+ in the filtrate lumen as a reservoir for H+
How does pH vary across the nephron?
Falls
