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Flashcards in CO2 Transport and pH homeostasis Deck (14)
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forms of CO2 in blood that make up partial pressure

dissolved CO2 - 5%
bicarbonate (HCO3-) - 90%
carbamino Hb (bound to N terminus of Hb) - 5%
carbonic acid (H2CO3) and carbonate (CO3-2) are negligible


what is the pH "window of life" and what are its usual values?

WoL - 6.8 to 8.0
usual - 7.4 +/- 0.03


rate of production of CO2

0.234 L/min = 0.01 mol/min = 14 moles/day


Jacobs-Stewart cycle in regular tissues and lungs
-what does this do to osmolarity?

1. CO2 from tissues diffuse to RBC, and either bind to Hb or convert to H2CO3 (via carbonic anhydrase)
2. H2O3 --> HCO3- + H+; the HCO3 can leave the cell (via an anionic exchanger with Cl- that doesn't need ATP) while the H+ can displace O2 on Hb
3. O2 leaves RBC to tissues
since CO2 and Cl- enter, but only HCO3- leaves (don't count O2), osmolarity increases so H2O increases too

all reactions are reversed in the lungs


imidazole buffer

a secondary blood buffer
histidine-Hb + H+ --> histidine+-Hb


what is the major blood buffer?

carbonid acid/bicarbonate buffer


what does increased PCO2 do to hemoglobin affinity for O2?

it weakens affinity for O2 (Bohr effect)


what does decreased pH do to hemoglobin affinity for O2?

it weakens affinity for O2 (Bohr effect)


what does increased temp do to hemoglobin affinity for O2?

it weakens affinity for O2


what 2 things does deoxygenation promote?

1. carbamino-Hb formation
2. H+ binding and formation of HCO3-


Haldane effect and Bohr effect and what they both mean

H: at any given PCO2, the CO2 content increases if blood is deoxygenated (PO2 decreases)
B: at any given PO2, O2 saturation decreases as PCO2 increases
-this minimizes acidification of venous blood, b/c deoxyhemoglobin is a weaker acid, and binds H+ more tightly, than oxyhemoglobin
-upon deoxygenation, more bicarbonate is formed, resulting in an upward shift in CO2 absorption curve
-upon binding to H+, Hb has reduced binding affinity for O2


what would isovolemic anemia do to total CO2 in the blood

nothing, b/c of Haldane effect
-RBC decreases, so less Hb, and H+ binding activity is reduced
-also PO2 decreases


Henderson-Hasselbach equation for carbonic acid

pH = pKa + log [HCO3-]/[CO2]


what does the bicarbonate titration curve tell you? why is this not so in real life?

at pKa, large fluctuations in acid/base would have little change in pH
-but at physiological pH, small fluctuations would cause large changes in pH
-if CO2 built up, pH would decrease and cause acedemia
-this doesn't happen in the body, because CO2 is constantly leaving the system, so pH changes little

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