Carbon Dioxide Transport

Question 1

In what 3 ways is CO2 transported, and what percentage does each method account for?

Answer 1

-5% dissolved in plasma
-10% associated with Hb to form carbaminohaemoglobin
-85% transported as hydrogen carbonate ions

Question 2

What is the symbol for hydrogen carbonate ions?

Answer 2

HCO3-

Question 3

1st step of CO2 transport as hydrogen carbonate ions

Answer 3

CO2 enters erythrocyte and dissolves in water of cytoplasm to form carbonic acid

Question 4

What is the name of the enzyme used when Co2 dissolves to form carbonic acid?

Answer 4

carbonic anhydrase catalyst

Question 5

Symbol equation for 1st stage

Answer 5

CO2 + H2O = H2CO3

Question 6

2nd step of CO2 transport as hydrogen carbonate ions

Answer 6

Carbonic acid releases H+ protons and hydrogencarbonate ions

Question 7

Symbol equation for 2nd step

Answer 7

H2CO3 = HCO3- + H+

Question 8

3rd step of CO2 transport as hydrogen carbonate ions

Answer 8

hydrogen carbonate ions (HCO3-) diffuse out of the erythrocyte

Question 9

4th step of CO2 transport as hydrogen carbonate ions

Answer 9

chloride shift occurs-CL- diffuses into cell to balance charge

Question 10

5th step of CO2 transport as hydrogen carbonate ions

Answer 10

H+ ions bind with haemoglobin to form haemoglobinic acid

Question 11

Symbol equation for 5th step

Answer 11

H+ + Hb = HHb

Question 12

How is the binding of H+ ions to Hb possible? (dissociation)

Answer 12

oxyhaemoglobin dissociates under influence of hydrogen ions

Question 13

Symbol equation for dissociation of oxyhaemoglobin

Answer 13

HbO8=Hb + 402

Question 14

What happens to the oxygen that is replaced by hydrogen ions in the haemoglobin?

Answer 14

oxygen is released into the blood plasma

Question 15

Explain the Bohr effect

Answer 15

-idea that when the concentration of CO2 is increased, more H+ ions are dissociated which reduces the affinity of Hb for oxygen
-therefore, more oxygen dissociates from oxyhaemoglobin

Question 16

How do respiring tissues lead to oxygen dissociation?

Answer 16

-more CO2 is produced
-more carbonic acid is formed
-more H+ ions dissociated
-more competition for haemoglobin
-more oxygen dissociation

Question 17

Describe how the oxygen dissociation curve will change when CO2 levels are increased

Answer 17

curve will shift to the right

Question 18

Explain why the curve shifts this way

Answer 18

-a higher PO2 is required to saturate Hb due to H+ competition (eg pO2 of 8=80% saturation but previously = 90%)
-a shift to the right indicates low O2 affinity