Transport of Carbon Dioxide

1. Dissolved in Blood Plasma (7-10%)
2. Bound to Hemoglobin (20-30%)
1. carbaminohemoglobin - Car Diox binds to an amino acid on the polypeptide chains
2. Haldane Effect - the less oxygenated blood is, the more Carb Diox it can carry
• tissues - as Ox is unloaded, affinity for Carb Diox increases
• lungs - as Ox is loaded, affinity for Carb Diox decreases, allowing it to be released
3. Bicarbonate Ion Form in Plasma (60-70%)
1. Carbon Dioxide combines with water to form Bicarbonate
• CO2 + H2O <==> H2CO3 <==> H+ + HCO3-
2. carbonic anhydrase - enzyme in RBCs that catalyzes this reaction in both directions
• tissues - catalyzes formation of Bicarbonate
• lungs - catalyzes formation of Carb Diox
3. Bohr Effect - formation of Bicarbonate (through Carbonic Acid) leads to LOWER pH (H+ increase), and more unloading of Ox to tissues
• since hemoglobin "buffers" to H+, the actual pH of blood does not change much
4. Chloride Shift - chloride ions move in opposite direction of the entering/leaving Bicarbonate, to prevent osmotic problems with RBCs
4. Carbon Dioxide Effects on Blood pH
1. carbonic acid-bicarbonate buffer system
• low pH -----> HCO3- binds to H+
• high pH -----> H2CO3 releases H+
2. low shallow breaths -----> HIGH Carb Diox -----> LOW pH (higher H+)
3. rapid deep breaths -----> LOW Carb Diox ----->HIGH pH (lower H+)

Category: Physiology Notes