Haemoglobin Flashcards
What is the structure of haemoglobin?
- 4 polypeptide chains
- each polypeptide chain associated with a haem group
- each haem group contains an iron ion in the centre which binds to oxygen
What does affinity mean?
The degree to which a substance tends to combine with another
Features of haemoglobin with a high affinity for oxygen
Will bind to oxygen easily but release less easily
Features of haemoglobin with a low affinity for oxygen
Will not bind to oxygen easily but will release it easily
What is partial pressure?
The amount of gas present in a mixture of gases is measured by its contribution to the total pressure of the gas mixture (kPa)
Explain how haemoglobin associates with oxygen in the lungs
- High partial pressure of O2
- O2 gets pressed onto haemoglobin molecules in RBCs so association occurs
- Haemoglobin leaves lungs fully saturated
Explain how haemoglobin dissociates with oxygen in respiring cells
- Low partial pressure of O2
- O2 dissociates from haemoglobin
- Diffuses into respiring cells
- Haemoglobin now unsaturated
Define cooperative binding
Binding of one molecule affects the binding affinity of subsequent molecules
Factors affecting oxygen dissociation curve
- The organism’s environment (O2 availability)
- How metabolically active the organism is
If the oxygen dissociation curve is shifted left does the haemoglobin have a higher or lower affinity for oxygen?
Higher
Which way would the oxygen dissociation curve shift for a metabolically active organism?
Right - lower affinity in order to supply sufficient oxygen
What is The Bohr Effect?
Carbon dioxide reduces haemoglobin’s affinity for oxygen.
What 3 things cause the Bohr Effect?
- High CO2 concentration
- Low pH
- High temperature
