Phys - Transport of CO2/Acid-Base Balance Flashcards
Normal rate of CO2 production
200 ml/min
3 ways in which CO2 is transported in blood
- Dissolved
- Carbamylation to protein
- Bicarb
Is more O2 or CO2 dissolved in blood? Why?
CO2; higher solubility; C=alpha*P
Two proteins to which CO2 is most often carbamylated
Hb and albumin
What functional group binds CO2 during carbamylation?
-NH2
How does O2 binding to Hb differ from CO2 binding?
O2 binds to Fe2+ of heme, while CO2 binds to -NH2 of heme
Where does CO2 from bicarb? Why?
RBC; plasma doesn’t have carbonic anhydrase
Which transport mechanism of CO2 predominates?
Bicarb
In blood, O2 mainly transported as ___ while CO2 mainly transported as ___
HbO2; bicarb
Rate limiting step in CO2 transport
Hydration (CO2+H2O –> H2CO3)
Requires CA
Explain process of CO2 transport from tissue to blood
- CO2 diffuses across tissue and RBC membranes (some dissolves in blood)
- CO2 is hydrated via CA once in RBC, forming HCO3- and H+
- H+ buffered by deoxyHb
- HCO3- forced out of cell since H+ not available to form carbonic acid
- HCO3- exchanged for Cl-/H2O to keep charge balance
What is Hamburger’s phenomenon?
Cl- that enters RBC in exchange for HCO3- drags water with it, causing RBC to swell
Name of HCO3-/Cl- anion exchange protein
Band three protein
Why does H+ bind deoxyHb? What other effect does this have?
To prevent acidification of RBC
Right shifts O2-Hb curve
Majority of H+ in venous blood carried as:
Bound to deoxyHb
Describe process of CO2 transport from RBC to lung
- CO2 dissociates from carbaminohemoglobin
- HCO3- reenters cell and forms CO2 with dissociated H+
- CO2 diffuses across RBC and alveolar membranes
- CO2 exhaled
Hb has more affinity for CO2 or O2?
CO2 (which right shifts O2-Hb curve)
Difference between CO2 and O2 dissociation curves:
CO2 curve is:
- Steeper (small change in PCO2=massive change in CO2 content)
- Higher (more CO2 in blood than O2)
- Linear (changes in PCO2 over broad range have same effect on CO2 content; no cooperativity)
Haldane effect
Changes in O2 saturation of Hb will shift CO2 dissociation curve
Left shift of CO2 curve means
Decreased O2Hb (more affinity for CO2)
Right shift of CO2 curve means
Increased O2Hb (less affinity for CO2)
Why does deoxygenation of blood left shift CO2 curve?
H+ can bind to Hb and CO2 binds Hb with greater affinity than O2
What is the difference between Bohr effect and Haldane effect?
Bohr effect refers to H+ effect on shift of O2 curve
Haldane effect refers to O2 effect on shift of CO2 curve
From right to left atrium, PO2 increases from 40-100 mmHg and PCO2 decreased from 46-40 mmHg. Respiratory quotient is 0.8 but a 6 mmHg change in PCO2 is matched with 60 mmHg change in PO2. How can this happen?
The CO2 curve is linear so small change in PCO2 = massive change in CO2 content. The O2 curve is sigmoidal, so the magnitude of the change in O2 content matches the magnitude of the change in CO2 content.
