Haemoglobin

Question 1

What are haemoglobins?

Answer 1

a group of chemically similar molecules found in many different organisms

Question 2

What is haemoglobin?

Answer 2

a protein with a quaternary structure that transports oxygen

Question 3

What is the structure of haemoglobin?

Answer 3

• made up of 4 polypeptide chains (quaternary structure) held together by bonds
• curled up → hydrophilic chains face outwards and hydrophobic side chains face inwards which makes it soluble and good for transport in the blood.
• each chain has a haeme group which contains an iron ion

Question 4

How does haemoglobin transport oxygen in humans?

Answer 4

• in the lungs there is a high saturation and partial pressure of oxygen so haemoglobin has a high affinity for oxygen so the oxygen loads to form oxyhaemoglobin
• at the respiring tissues there is a low partial pressure of oxygen so haemoglobin has a low affinity for oxygen causing the oxyheamogobin to dissociate and oxygen is unloaded into respiring tissues where there is a low saturation

Question 5

What is the equation for oxygen transport?

Answer 5

Hb + 4O2 → Hb (O2) 4
←
(Reversible reaction)

Question 6

Why are dissociation curves S shaped?

Answer 6

• when haemoglobin combines with first oxygen molecule its shaoe alters in a way that it makes it easier for other oxygen molecules to join due to cooperative nature of oxygen
• graph flattens towards the end → joining 4th molecule is harder

Question 7

What is the Bohr effect?

Answer 7

• when CO2 dissolves in water it forms carbonic acid which breaks down and releases hydrogen ions which can diffuse into red blood cells
• this changes the shape of the haemoglobin so oxyhaemoglobin breaks down faster (more 02 for respiration when exercising)
• the carbonic acid changes the blood pH which makes the haeomglobin to lose their oxygen more readily

Question 8

What happens to the dissociation cure when there is a high CO2 level?

Answer 8

shift to the right
- the affinity for oxygen decreases as the acidic CO2 changes shape of the haemoglobin slightly

Question 9

What is the dissociation curve for low oxygen environments?

Answer 9

Shifts to the left
- Hb has high affinity for oxygen so pick it up more readily but releases it less readily (only releases oxygen when the partial pressure of oxygen is very low)

Question 10

What is the dissociation curve for high activity levels?

Answer 10

Shifts to the right
- Hb has low affinity for oxygen as the Hb needs to easily unload the oxygen so its readily available for respiration

Question 11

What is the dissociation curve for smaller mammals?

Answer 11

Shift to the right
- small animals have high SA:Vol so they lose heat quickly and they have high metabolic rates to keep warm
- high demand for O2 so have lower affinity do it is easily unloaded

Question 12

What is the dissociation curve for foetal haemoglobin?

Answer 12

Shift to the left
- higher affinity for oxygen than maternal Hb
- maternal oxyhaemoglobin will dissociate in placenta and foetal Hb loads with O2 which allows foetus to get oxyegn for its respiring tissues
- lungs are not respiring but lung tissue needs to be provided with O2 to allow cells to grow and develop