Oxygen transport

Question 1

Describe the structure of haem

Answer 1

Haem is a porphyrin ring around single ferrous form of iron (Fe2+), which comes out of plane of the ring to bind o2.

Question 2

Describe the structure of haemoglobin?

Answer 2

2α + 2β chains (each have 1 haem & 1 globin) - quarternary structure

Question 3

What happens when one oxygen binds to haemoglobin?

Answer 3

It increases the affinity for more oxygen by changing it from a tensed to relaxed state.

(Fe2+ associated with amino acid residue histadine - When one oxygen binds, it pulls the iron ion down, pulling the iron in plane with the haem ring that is attached by histadine residue to the F helix, which changes shape from a tensed to a relaxed position, increasing affinity for oxygen. )

Question 4

How is Hb saturated in anaemia?

Answer 4

Hb is still 100% saturated, but low Hb levels

Question 5

What is the ideal oxygen saturation?

Answer 5

8 kPa = 90%

Question 6

What factors shift the oxygen dissociation curve to the right, favouring tissues where O2 needs to be offloaded?

Answer 6

• Increased temperature
• Acidic pH
• High CO2 levels
• 2,3-DPG

Question 7

What is 2,3-DPG?

Answer 7

Adaptive response – levels increase in hypoxia – binds to Hb to stabilise tensed state → deliver more O2 to tissues

Question 8

What is the Bohr effect?

Answer 8

In acid conditions, the oxygen dissociation curve shifts along the pO2 (x) axis

Question 9

What is the Haldane effect?

Answer 9

Increasing O2 binding to Hb (in lungs) reduces affinity for CO2 & H+ by modifying the quarternary structure.
This causes CO2 offloading in the lungs.

Question 10

What adaptations occur in chronic hypoxia in an attempt to increase O2 delivery in tissues?

Answer 10

• Increase 2,3-DPG
• Increase EPO
• Increase tissue capillary density
• Increase ventilation