haemoglobin

Question 1

Describe how haemoglobin normally loads oxygen in the lungs and unloads it in a tissue cell.

Answer 1

• Oxygen combines (reversibly) to produce oxyhaemoglobin
• one haemoglobin may transport 4 molecules of oxygen
• high partial pressure of oxygen concentration in LUNGS
• haemoglobin (almost) 95% / 100% saturated
• unloads at low oxygen tension (in TISSUES)
• presence of carbon dioxide displaces curve further to right ->allows more O2 to be unloaded
• increase temp allows more O2 to be unloaded
• low pO2 / increase CO2/ increase acid occur in vicinity of respiring tissue

Question 2

Explain how oxygen in a red blood cell is made available for respiration in active tissues.

Answer 2

• CO2 (increased) respiration;
• (increased) dissociation oxygen from haemoglobin;
• Low partial pressure in tissues
• Oxygen diffuses from red blood cells to tissues

Question 3

The oxygen dissociation curve of the foetus is to the left of that for its mother. Explain the advantage of this for the foetus.

Answer 3

• Higher affinity -> loads more oxygen
• At low/same/high partial pressure
• Oxygen moves from mother to fetus

Question 4

Explain how oxygen is loaded, transported and unloaded in the blood. (6)

Answer 4

• Haemoglobin carries oxygen
/ has a high affinity for oxygen
/ oxyhaemoglobin;
• In red blood cells
• Loading in lungs at high p.O2
• Unloads/ dissociates releases to respiring tissues at low p.O2
• Unloading linked to higher carbon dioxide (concentration)

Question 5

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.

Explain why

Answer 5

1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin
   [conformational shift caused]
2. Leads to uncovers second / another binding site
   OR Uncovers another iron / Fe / haem group to bind to;

Question 6

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin

Answer 6

1. Increases oxygen dissociation/unloading
   OR Deceases haemoglobin’s affinity for O2
2. (By) decreasing (blood) pH

Question 7

How to calculate percentage saturation of haemoglobin?

Answer 7

(oxygenated Hb / maximum saturation) × 100

Question 8

Explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins (5)

Answer 8

1. Smaller mammal has greater surface area to volume ratio
2. So more heat loss
3. So greater rate of respiration
4. Oxygen required for aerobic respiration
5. Haemoglobin releases more oxygen OR haemoglobin has lower affinity for oxygen