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REN/RESP - CO2 Transport
Terms in this set (16)
CO2 is carried in the blood in three forms - what are they? What percent of the total CO2 content do each represent?
1. dissolved CO2 - 5%
2. carbaminohemoglobin - 3%
3. bicarbonate (HCO3-) - 90%
Which form of CO2 in the blood is the most important?
CO2 binds to Hb at a different site than O2 binds to hemoglobin. How does O2 affect Hb's affinity for CO2?
O2 bound to Hb changes its affinity for CO2, such that when less O2 is bound, the affinity of Hb for CO2 increases. (i.e. the Haldane effect)
Explain the mutual effects of O2 and CO2 on each others' binding to Hb. Why does it make sense?
CO2 binding to Hb reduces its affinity for O2. While O2 bound to Hb changes its affinity for CO2, such that when less O2 is bound, the affinity for Hb for CO2 increases.
These effects makes sense because in the tissues, as CO2 is produced and binds to Hb, Hb's affinity for O2 is decreased and it releases O2 to the tissues more readily; in turn, release of O2 from Hb increases its affinity for the CO2 that is being produced in the tissues.
Enzyme that catalyzes both the hydration of CO2 and the dehydration of H2CO3:
_______ is found in high concentration in red blood cell.
Carbonic anhydration -- it catalyzes the hydration of CO2 to form H2CO3
In RBCs, H2CO3 dissociates into H+ and HCO3-. While the HCO3- produced is exchanged for Cl- in the plasma, the H+ remains in the red blood cells -- how is the cell able to control its pH?
The H+ that remains in the RBC's where it will be buffered by deoxyhemoglobin.
Why is deoxyHb a better buffer for H+ than oxyHb?
By the time the blood reaches the venous end of the capillaries, Hb is conveniently in its deoxygenated form (i.e. it has released O2 to the tissues)
The Bohr effect states that an increased H+ concentration causes a right shift of the O2-Hb dissociation curve, which causes Hb to unload O2 more readily in the tissues; thus, the H+ generated from tissue CO2 causes Hb to release O2 more readily to the tissues.
Describe how CO2 is expired in the lungs, beginning with HCO3- in the plasma:
1. H+ is released from its buffering sites on deoxyHb
2. HCO3- enters the RBC's in exchange for Cl-
3. H+ and HCO3- combine to form H2CO3
4. H2CO3 dissociates into CO2 and H2O.
5. The regenerated CO2 and H2O are expired by the lungs.
In a right to left shunt, hypoxemia always occurs - True or False?
True -- because a significant fraction of the CO is not delivered to the lungs for oxygenation.
Why is having an individual with a right-to-left shunt breathe 100% O2 a useful diagnostic tool?
Hypoxemia caused by a right to left shunt cannot be corrected by having a person breathe a high O2 gas because the shunted blood never goes to the lungs to be oxygenated.
The shunted blood will continue to dilute the normally oxygenated blood, and no matter how high the alveolar PO2, it cannot offset this dilution effect.
Describe the importance of the chloride shift in the transport of CO2 by the blood:
Identify the enzyme that is essential to normal CO2 transport by the blood and its location:
Define the interplay between CO2 and O2 binding on hemoglobin that causes the Haldane effect:
Describe the effect of diffusion, intrapulmonary shunt, and ventilation to perfusion abnormalities on PaCO2:
Define respiratory acidosis and alkalosis. Give a clinical example of each.
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