Acid base part 3 Flashcards
CO2 is transported in the blood as 1 of 3 things:
1) CO2
2) Carbonic acid H2CO3
3) Bicarbonate ion HCO3-
What is the most important buffer system in the ECF?
Bicarbonate buffer system
The Bicarbonate buffer system consists of:
a weak acid H2CO3, and a weak base HCO3-
Is bicarb readily available?
yes
What makes bicarb an open system?
because the components of the bicarb system can be used independently of each other.
-Example: CO2 by the lungs and Bicarb by the kidneys
What organ produces bicarb?
The pancreas
What is the carbonic acid reaction? Is it slow or fast?
CO2 + H2O = H2CO3
this reaction is slow without an enzyme
bicarbonate reaction
Dissociation of H2CO3 = H+ + HCO3-
What is the bicarbonate/carbonic acid reaction called? is it reversible?
Hydration reaction
The reaction is reversible
what enzyme catalyzes the carbonic acid reaction?
Carbonic anhydrase
Where is carbonic anhydrase abundant?
1) Within red blood cells
2) ln the walls of lung alveoli
3) epithelial cells of renal tubules
Where is phosphate buffer important?
1) intracellularly
2) tubular filtrate of the kidneys
What is the weak acid and conjugate base of phosphate buffer?
weak acid, monosodium phosphate, NaH2PO4
conjugate base, disodium phosphate, Na2HPO4
what happens to phosphate buffer when it reacts with a strong acid?
- a weaker acid and salt is formed
HCl + Na2HPO4 = NaH2PO4 + NaCl
what happens to phosphate buffer when it reacts with a strong base?
- a weaker base and water is formed
NaOH + NaH2PO4 = Na2HPO4 + H2O
What is the second line of defense for acid-base balance?
the lungs (the respiratory system) (fast)
Which system has more capacity to buffer? Respiratory or chemical systems?
Respiratory
What is the third line of defense for acid-base balance?
the kidneys (slow)
What is the most potent acid-base regulator?
the kidneys - takes days to respond
How do the kidneys help acid-base?
excretes basic or acidic urine
- creates HCO3-
- filtrates bicarb HCO3-
- secretes a lot of H+
how do kidneys add to real loss of acid or base?
changes in the amount of HCO3- filtered
changes in the amount of H+ secreted
How do the kidneys regulate [H+] in the ECF? (3 ways)
1) Secrete H+
2) Reabsorbs filtered HCO3-
3) Production of new HCO3-
Secretion of H+ occurs in the epithelial cells of 3 places:
1) proximal tubes (mostly)
2) distal tubules
3) collecting ducts
