Haemoglobin

Question 1

Definition of:

1) Affinity
2) Saturation
3) Loading/Unloading

Answer 1

1) Natural attraction to something
2) How much O2 is combined with haemoglobin
3) When O2 is taken up/released

Question 2

How to calculate percentage saturation of haemoglobin with oxygen?

Answer 2

Oxygenated Haemoglobin
————————————— x100
Maximum Saturation

Question 3

Names of axis on dissociation curve?

Answer 3

• Percentage saturation of haemoglobin to oxygen (%)
• Partial pressure of oxygen (KPa)

Question 4

Explain how oxygen is loaded, transported + unloaded in the blood? (6)

Answer 4

• Haemoglobin carries oxygen/ high affinity for O2
• In red blood cells
• Loading in the lungs
• At high partial pressure of O2
• Unloads to respiring tissues
• At low partial pressure

Question 5

The oxygen dissociation curve of the foetus is to the left of its mother.
Explain the advantage of this for the foetus? (3)

Answer 5

• Higher affinity/loads more oxygen
• At low/same partial pressure
• Oxygen moves from mother to foetus

Question 6

Heat from respiration helps mammals to maintain a constant body temperature.
Use the information to explain the relationship between the surface area:volume ratio of mammals + the oxygen dissociation curves of their haemoglobin? (5)

Answer 6

• Smaller mammal gas greater surface area to volume ratio
• So more heat is lost
• So has greater rate of respiration/metabolism
• Oxygen required for aerobic respiration
• Haemoglobin releases more oxygen/ haemoglobin has lower affinity

Question 7

Describe how haemoglobin normally loads oxygen in the lungs + unloads it in a tissue cell? (6)

Answer 7

• Oxygen combines to produce oxyhemoglobin
• Each haemoglobin molecule may transport 4 molecules of O2
• High partial pressure of oxygen in lungs so high saturation
• Presence of CO2 increases oxygen dissociation
• So more O2 unloaded
• Low partial pressure/ increase CO2 in respiring tissue

Question 8

Explain how oxygen in red blood cells is made available for respiration in active tissues? (4)

Answer 8

• CO2 increased respiration
• So increases dissociation of oxygen from haemoglobin
• Low partial pressure in tissues
• Oxygen diffuses from r.b.c. to tissues

Question 9

Explain why binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecules to bind? (2)

Answer 9

• Binding of first oxygen changes tertiary/quaternary structure of haemoglobin
• Which uncovers another binding site

Question 10

Describe + explain the effect of increasing CO2 conc. on the dissociation of oxyhemoglobin? (2)

Answer 10

• Increases unloading/ decreases haemoglobin’s affinity for O2
• By decreasing blood pH

Question 11

If the dissociation cure is to the left then… (3)

Answer 11

• Loads more oxygen
• At a lower partial pressure
• Haemoglobin has higher affinity for O2

Question 12

If the dissociation curve is to the right then… (5)

Answer 12

• Loads less oxygen
• For more aerobic respiration so more ATP
• More heat energy released
• At the same partial pressure
• Haemoglobin has lower affinity for O2

Question 13

In oxygen dissociation curve, if higher partial pressure of CO2 then…

Answer 13

• Saturation of haemoglobin decreases
• Curve shifts to the right as affinity for O2 is lower