Transport Of O2 And Co2

Question 1

Structure of haemoglobin

Answer 1

• globular conjugated protein
• 4 polypeptide chains so can bind to 4 oxygen molecules
• hb + 4o2 equals hb(o2)4

Question 2

How is o2 transported

Answer 2

1) steep conc when erythrocytes enter capillaries, steep conc of air inside alveoli and inside erythrocytes
2) therefore o2 moves in and binds to hb
3) every time o2 binds, hb changes tertiary structure making it easier for other o2 to bind ( positive cooperatively)
4) free o2 conc in erythrocyte stays low so steep gradient maintained
5) when blood reaches body tissue, its lower o2 content than erythrocytes therefore o2 moves out down con gradient
6)when each is removed, changes shape again so easier to remove o2

Question 3

What does o2 dissociation curve show

Answer 3

• the affinity of hb for o2
• each time an o2 is attached, the higher po2 so the higher the affinity

Question 4

The effect of co2 on o2 dissociation curve

Answer 4

• as the co2 partial pressure increases, hb gives up o2 much easier ( known as Bohr effect)
• in active tissues with high partial pressure of co2, hb gives up o2 much easier.
• in lungs where co2 proportion is low, hb binds to o2 much easier.
• at higher partial pressure of co2, curve shifts right

Question 5

How is co2 transported

Answer 5

• 5% dissolved in blood plasma
• 10-20% combine with hb to form carboaminohaemoglobin
• 75-85% converted into hc03- in cytoplasms of blood cells

Question 6

How is hydrogen carbonate ions formed

Answer 6

-co2 + water form carbonic acid H2C03
- H2CO3 dissociates into h+ and HCO3-
-carbonic anhydrase is the enzyme that speeds up this reaction

Question 7

What happens after hydrogen carbonate ions are produced

Answer 7

• hb acts as a buffer and removes h+ forming haemoglobinic acid and cl- moves in to maintain ph