Heamoglobin

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 mol transports 4 molecules of oxygen/8atoms
* high partial pressure of oxygen concentration in lungs;
* haemoglobin 95% 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

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. Creates / leads to / uncovers second / another binding site OR Uncovers another iron / Fe / haem group to bind to;

Question 6

explain how surface area to volume ration of an organism is related to its metabolic rate

Answer 6

small org= mouse
higer surface are : vol ratio
so easier to lose heat due to large surface area so requires high metabolic rate in order to generate heat to stay warm (so needs more o2 hence oxygen curve to the right as lower affinity so unload faster at RT)

small sa:vol harder to lose heat