transport of carbon dioxide

Explain how carbon dioxide is transported

1. In solution in the plasma - 5%

2. Bound to Haemoglobin as carbamino-Haemoglobin - 10%

3. As the hydrogen carbonate ion HCO3- - 85%

Some remains in the red blood cells but most reacts - see next fc

Explain the stages of reactions in red blood cells of co2 to dissociate oxygen

1. Carbon dioxide diffuses from blood plasma from body tissues into red blood cells by simple diffusion.

2. Carbonic anhydrase catalyses the combination of carbon dioxide and water (dissolved in water) to form carbonic acid

3. This dissociates into H+ ions and HCO3- ions

4. The hydrogen carbonate ions diffuse out via facilitated diffusion into plasma

5. This means that to maintain the electrochemical neutrality of the cell (now that it is positive with H+ ions), chloride ions which are negative diffuse into cell via facilitated diffusion - CHLORIDE SHIFT

6. H+ ions cause oxyhaemoglobin to dissociate into oxygen and Haemoglobin and outcompetes it to combine with Haemoglobin to make HHB

7. Oxygen is now leaves this is the lower affinity when Co2 is there

Explain how this links to the Bohr effect

More carbon dioxide means more H+ ions so the more oxygen is released from oxyhaemoglobin

So the higher the pp of co2 the lower the affinity for oxygen and due to the high concentration of co2 in respiring tissues due to respiration means the lower affinity and more dissociation in respiring tissues - especially with higher metabolic rate as more co2 so explains lugworms

So dissociation can take place at a higher pp as more co2 will be produced if more o2 from respiration so more dissociation

Done!