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
• Each haemoglobin molecule/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/increases oxygen dissociation
• Allows more O2 to be unloaded
• Increase temp/acidity allows more O2 to be unloaded
• Low pO2/increase CO2/increase term/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/plasma
Oxygen diffuses from r.b.c. 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/pO2
• Oxygen moves from mother/to foetus

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/uptake/association in lungs at high p.O2
• Unloads/dissociates/releases to respiring cells/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. Uncovers second/another binding site OR Uncovers another 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/more oxygen dissociation/unloading OR decreases haemoglobin’s affinity for O2
2. (By) decreasing (blood) pH/increasing acidity