Transport of carbon dioxide in the blood

Question 1

Whats the 1st step of transporting CO2 in the tissues?

Answer 1

CO2 reacts with water to form carbonic acid, carbonic anhydrase catalyses this reaction

Question 2

Whats the 2nd step of transporting CO2 in tissues?

Answer 2

Carbonic acid dissociates to form hydrogen carbonate ions + hydrogen ions

Hydrogen ions combine with haemoglobin (that acts as buffer) to form haemoglobinic acid

Question 3

Whats the 3rd step for transporting CO2 in tissues?

Answer 3

Hydrogen carbonate ions move out of RBCs into plasma by diffusion down conc gradient

Causes imbalance of charge, so chloride ions move into RBCs to maintain electrical balance

Known as chloride shift

Question 4

Whats the 4th step for transporting CO2 in tissues?

Answer 4

By converting CO2 into hydrogen carbonate ions, this maintains conc gradient for CO2 to diffuse into RBCs from respiring tissues

Question 5

1st step for transporting CO2 in lungs:

Answer 5

Low conc of CO2, carbonic anhydrase catalyses reaction, breaking down carbonic acid into CO2 and H2O

Question 6

2nd step of transporting CO2 in lungs:

Answer 6

Hydrogen carbonate ions move back into RBCs + react with hydrogen ions to form more carbonic acid

Question 7

3rd step for transporting CO2 in lungs:

Answer 7

When this is broken down, releases CO2, which diffuses out of blood into lungs

Question 8

4th step of transporting CO2 in lungs:

Answer 8

Chloride ions diffuse out of RBCs back into plasma down electrochemical gradient

Question 9

What are the 3 different ways of transporting CO2?

Answer 9

• 5% dissolved in plasma
• 10-20% combined with amino groups in polypeptide chains of haemoglobin to form carbaminohaemoglobin
• 75-85% converted to hydrogen carbonate ions in cytoplasm of RBCs