Term
| what is the normal arterial plasma pH? |
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Definition
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Term
| Why does the partial pressure of CO2 stay the same (around 40 mmHg) despite changes of acid/base concentrations in the blood? |
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Definition
| The amount of bicarbonate is altered to fix acid base problems, not CO2 |
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Term
| Are CO2 and bicarbonate excretion dependent or independent of each other? |
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Definition
| They are independent. CO2 excretion is under pulmonary control and bicarbonate secretion is under renal control |
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Term
| What is the Law of Mass Action? |
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Definition
The Law of Mass Action is one example of Le Chatelier's principle, that the equilibrium in a chemical system responds to a change in concentration, temperature, or pressure by shifting in the direction which partially counteracts the imposed perturbation.
**For our purposes, it is how our body reacts to proton concentration changes in the arterial space |
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Term
| Do mass action shifts work in open body systems? |
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Definition
| No, only in closed body systems |
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Term
| How does the kidney respond to acidosis? |
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Definition
| reabsorbs bicarbonate and secretes protons (one for one) |
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Term
| How much higher is the capacity of the lungs processing metabolic CO2 vs the ability of the kidneys to process HCO3 and H+? |
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Definition
| The lungs are 150x more efficient at getting rid of high levels of CO2 |
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Term
| Where is most of the HCO3 reabsorbed in the nephron? why? |
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Definition
| 80% of bicarbonate is reabsorbed in the proximal tubule because carbonic anhydrase is found in the brush border |
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Term
Where is most of the H+ secreted in the nephron? |
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Definition
| distal tubules and collecting duct |
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Term
| What does carbonic anhydrase do? |
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Definition
| Carbonic anhydrase accelerates the CO2 hydration reaction (forward rxn) and also accelerates the CO2 dehydration reaction going the other way. Which reaction it catalyzes depends on concentration of CO2 or bicarbonate (mass action shifts) |
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Term
| where does NH3 (and NH4+) come from? |
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Definition
NH3 + glutamate ---> glutamine
NH3 is a metabolic product of glutamine
NH3 + H+ ---> NH4+
NH3 combines with H+ in the proximal to form NH4+ which accounts for almost all of the H+ secreted in proximal tubule (otherwise, there is little net secretion of H+ before distal nephron) |
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Term
| What is the difference between Type A and Type B intercalated cells? |
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Definition
Type A cells secrete protons and transport bicarbonate into the interstitium
Type B cells secrete bicarbonate and transport protons into the interstitium
(These two types can switch back and forth because their transporters can be switched between apical and basolateral membranes) |
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Term
| How much more acidic is the distal nephron than the arterial plasma? |
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Definition
1000x conc of protons in the distal nephron
plasma pH = 7.4
distal nephron/urine pH = 4.4 |
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Term
| What are the three forms of secreted protons in the urine? |
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Definition
(1) free protons which generate the urinary pH
(2) titratable acids (especially dihydrogen phosphate)
(3) ammonium ions (which are diffusion trapped) |
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Term
| Where does ammoniagenesis occur? |
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Definition
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Term
| Where is glutamine synthesized? What are the two main components? |
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Definition
in the liver
NH4+ + bicarbonate = glutamine |
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Term
| Where does ammonium reabsorption occur? What protein transporter is responsible for the majority of reabsorption? |
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Definition
thick ascending limb
NKCC multiporter (ammonium is substituted for K+) |
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Term
| Where is ammonium secreted back into urine? What protein transporter is used? |
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Definition
common collecting duct (inner medulla)
Na/K ATPase (ammonium substitutes for K+) |
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Term
| What are the pKas of sulfuric acid, dihydrogen monophosphate and ammonia? |
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Definition
sulfuric acid pKa = 1.9
dihydrogen monophosphate pKa = 6.8
ammonia pKa = 9.3 |
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Term
| Which acid is always in its dissociated form (basic form) in urine? |
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Definition
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Term
| Which acid is titratable in the urinary pH range (4.4 to 7.4) ? |
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Definition
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Term
| Which acid is always in its undissociated form (acid form) in urine? |
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Definition
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