| Structure of haemoglobin | - Large protein, quaternary structure
- Made up of 4 polypeptide chains
- Each chain has a haem group
- High affinity for oxygen |
| Haem group | - Has iron ions
- Gives haemoglobin its red colour |
| Affinity for oxgyen meaning | - Tendency to combine with oxygen |
| High affinity for oxygen | - Each molecule carries 4 oxygen molecules
- In lungs, oxygen binds to haemoglobin in red blood cells
- Forms oxyhaemoglobin |
| Reaction of forming oxyhaemoglobin | - Reversible reaction
- When oxygen leaves oxyhaemoglobin (dissociates from it) near body cells
- Turns back to haemoglobin |
| Reaction of haemoglobin and oxygen equation | Hb + 4O2 <-----> HbO8
haemoglobin + oxygen <-----> oxyhaemoglobin |
| Loading or association meaning | - Haemoglobin binding with oxygen
- Forms oxyhaemoglobin where there's a high pO2
- In humans, takes place in lungs |
| Unloading or dissociation meaning | - Oxyhaemoglobin releases its oxygen
- Where there is a lower pO2
- In humans, takes place in tissues |
| How high or low affinity of oxygen affects haemoglobin molecules | - The higher it is, the easier it is to take up oxygen, but the harder it is to release oxygen
- The lower it is, the harder it is to take up oxygen, but the easier it is to release oxygen |
| The role of haemoglobin | - Transports oxygen |
| 2 things must happen for haemoglobin to carry out its function | - Readily associate with oxygen at the surface where gas exchange takes place
- Readily disassociate from oxygen at tissues requiring it |
| How it achieves its function | - It changes its affinity for oxygen under different conditions
- Changes shape in the presence of different substances e.g. CO2
- The new haemoglobin shape binds more loosely to oxygen, releasing it easier |
| Why are there different haemoglobins | - Organisms have different types of haemoglobin with different oxygen transporting capacities
- Adaptation that helps organism survive in particular
environment |
| Organisms in environment with low concentration of oxygen | - Organisms have haemoglobin with higher affinity for O2 than humans, disassociation curve is to left of humans |
| Organisms in environment with high concentration of oxygen | - Organisms are very active, high O2 demand, have haemoglobin with lower affinity for oxygen than humans, curve is to the right of humans |
