Haemoglobin Flashcards
What is the structure of a haemoglobin molecule?
Primary structure- consists of four polypeptide chains.
Secondary structure- each of the polypeptide chains is coiled into a helix.
Tertiary structure- each polypeptide chain is coiled into a helix.
Quaternary structure- all four polypeptides linked together to form an almost spherical molecule.
What is each polypeptide of a heamoglobin molecule associated with?
A haem group which contains a Fe 2+ ion
Each Fe 2+ ion can combine with a single oxygen molecule.
How many oxygen molecules can be carried by a haemoglobin molecule?
4
What is the role of haemoglobin?
Readily associating with oxygen at the surface where gas exchange takes place.
Readily disassociating from oxygen at the tissues requiring it.
How does haemoglobin change its affinity for oxygen in different conditions?
Its shape changes in the presence of certain substances.
In the presence of CO2, the new shape of the haemoglobin molecule binds more loosely with oxygen- releasing it.
Region of body: Gas exchange surface
O2 conc: High
CO2 conc: Low
Affinity: High
Result: Oxygen attached
Region of body: Respiring tissues
O2 conc: Low
CO2 conc: High
Affinity: Low
Result: Oxygen released
Haemoglobin with a high affinity for oxygen…
Take up oxygen more easily but release it less readily.
Haemoglobin with a low affinity for oxygen…
Take up oxygen less easily but release it more readily.
Why does haemoglobin have different affinities for oxygen?
They have different shapes.
What is loading/associating?
The process by which haemoglobin combines with oxygen in the lungs.
What is unloading/disassociating?
The process by which haemoglobin releases its oxygen in the tissues.
