Carbon Dioxide Transport In Blood Flashcards
Forms of CO2 in blood
. Dissolved
. Carbaminio compound
. Bicarbonate
. Arterial blood has 48 ml/dl of CO2 and venous blood has 53 ml/dl
Dissolved CO2
. Blood PCO2 depends on amt CO2 physically dissolved in blood
. CO2 20x more soluble than O2
. Greater proportion of CO2 is carried in dissolved form than O2
. Only 5% of blood’s total CO2 content is carried in dissolved form
Carbamino compound
. HbCO2
. Reduce Hb has greater affinity for CO2 than oxy-Hb
. Unloading of O2 from Hb in systemic capillaries facilitates loading of CO2
. 5% blood’s total CO2 content is carried as this
Bicarbonate pathway
. 90% of blood’s total CO2 content carried in this
. CO2 + H2O H2CO3 -> H + HCO3 (catalyzed by carbonic anhydrase)
. Takes place w/in blood cells but can occur very slow in plasma
. HCO3 and H accumulate in RBC
The membrane transporter facilitates movement of HCO3 out and Cl in (Cl shift to maintain neutrality)but is impermeable to H
. HCO3 diffuses down its conc. Gradient out of RBC and into blood
Hardened effect
. H ions remain in RBC and bind w/ Hb that just release its O2 in systemic capillary
. Reduced Hb has greater affinity for H than oxy-Hb
. Removal of O2 from Hb inc. ability of Hb to bind w/ CO2 and CO2-generated H
. Effect is he fact that deoxygenation of Hb inc. it’s ability to carry CO2
CO2 uptake from blood
. Uptake into RBCs inc. as HCO3 and H conc. Inc.
. Inc. in osmotic pressure of RBCs draws H2O into cells
. RBC volume inc. slightly as it passes through systemic capillaries
CO2 exchange in lung
. CO2 diffuses down PCO2 gradient
. Removed from body during expiration
. Draws HCO3 ions rom plasma into RBCs where they follow reverse bicarbonate rxn to form dissolved CO2 and H2O
. CO2 diffuses out of RBC into plasma and then into alveoli
CO2 dissociation curve
. More linear relationship than O2
. The lower the PO2 the higher CO2 content in Hb for any given PCO2
. Due to reduced Hb having greater ability to bind H ions and bc reduced Hb is more likely to form carbamino compound
. In tissue capillaries the haldane effect causes inc. pickup of CO2 demo O2 removal
Effect of inc. PCO2 on amount of total CO2 carried by blood
. Inc. Dissolved CO2
. Inc. HCO3 formation
. Inc. carbamino compound
Effect of inc. Plasma protein conc. on amount of total CO2 carried by blood
Inc. plasma buffering power
. Inc. capacity for consuming H indirectly promotes formation of HCO3
Effect of inc. Plasma pH on amount of total CO2 carried by blood
. Inc. formation of HCO3 in plasma
. Inc pH inside RBC promotes formation of HCO3 and carbamino compound
Effect of inc. Hb conc. on amount of total CO2 carried by blood
. Inc. formation of carbamino compound
. Inc. buffering power inside RBC
. Inc. capacity for consuming H indirectly promotes formation of HCO3 and carbamino compounds
Effect of inc. PO2 on amount of total CO2 carried by blood
. Dec. buffering power of Hb due to Bohr effect
. Dec. capacity for consuming H indirectly restrains formation of HCO3 and carbamino compound
. Dec. formation of carbamino compound due to Bohr effect
Change in blood acidity during CO2 transport
. When CO2 enters blood it will combine w/ H2O to form H2CO3 that dissociates into H and HCO3
. PH will dec. slightly in tissues
. H that is formed will combine w/ blood buffers so it won’t dec. excessively
. As blood acquires CO2 in tissue capillaries, the pH of arterial blood inc. to 7.41
Respiratory acidosis
. Inc. PCO2 that reduces HCO3/PCO2 ratio
. Depresses pH
. An inc. in PCO2 can be caused by hypoventilation or a ventilation-perfusion inequality
