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;

• 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

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

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

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

Answer 6

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

Question 7

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

Answer 7

1. Increases dissociation of oxygen;
   Accept unloading/ release/reduced affinity for
   dissociation
   For aerobic respiration at the tissues/muscles/cells
   OR
   Anaerobic respiration delayed at the tissues/muscles/cells
   OR
   Less lactate at the tissues/muscles/cells;

Question 8

Give the formula when calculating percentage of saturation of haemoglobin with oxygen:

Answer 8

Oxygenated Hb
—————————- X100
Maximum saturation

Question 9

Define partial pressure of oxygen (pO2/kPa)

Answer 9

The amount of oxygen in a mixture of gases or a solution

Question 10

LOWER pO2 means…

Answer 10

LESS Hb is saturated

Question 11

Lower pO2 in…

Answer 11

Tissues when at rest

Question 12

Higher PO2 in…

Answer 12

Lungs (high saturation of Hb)

Question 13

pO2 in lungs:

Answer 13

Hb has a higher affinity for O2 at high pO2

Hb becomes fully saturated

Question 14

pO2 in respiring tissues:

Answer 14

Hb lower affinity for O2 at lower pO2

So oxyhaemoglobin starts to unload oxygen

To be used in aerobic respiration

Question 15

What is the effect of increase respiration on oxygen dissociation?

Answer 15

1. Tissue cells respirier aerobically reducing dissolved O2 in surrounding tissue fluid
2. Reduces the O2 to a lower level than normal
3. Oxygenated blood arriving with fully saturated Hb unloads MORE oxygen and MORE oxygen will be released from Hb to the tissue cells
4. Because surrounding pO2 is lower so Hb has an even lower affinity to oxygen

Question 16

Heat from respiration helps mammals to maintain a constant body temperature.

Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins.

Answer 16

Smaller mammal has greater surface area to volume ratio,

Smaller mammal/larger SA: Vol ratio more heat lost (per unit body mass);

Smaller mammal/larger SA: Vol ratio has greater rate of respiration/ metabolism;

Oxygen required for aerobic respiration;
(Haemoglobin) releases more oxygen / oxygen released more readily / hemoglobin has lower affinity;