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 / oxygen tension / 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 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/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

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

Answer 5

• 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 6

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

Explain why.

Answer 6

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

Question 7

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

Answer 7

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