Transport of Oxygen
Haemoglobin
Transported in erythrocytes (red blood cells)
Associates with oxygen to form oxyhaemoglobin (Hb(CO₂)₄)
Consists of 4 polypeptide chains in a quaternary structure
Each chain consists of a non-protein haem group each containing an iron ion (Fe2+)
which attracts and holds oxygen molecules
Haemoglobin has a high affinity for oxygen
Oxygen dissociates and leaves haemoglobin to be released into respiring tissues
Partial Pressure of Oxygen
Oxygen tension = oxygen concentration
Also called partial pressure of oxygen (pO₂) and measured in kilopascals (kPa)
Oxygen has a long diffusion distance to the haem group
Low pO₂ = low saturation
After one O₂ molecule binds to a haem group, a conformational change occurs in the
haemoglobin molecule
The shape changes and the haem groups move to the outside
Allows O₂ molecules to associate with ease
Approaching 100% saturation, diffusion gradient decreases and oxygen struggles to
associate
After birth there is a change in environment to higher oxygen tension so adult haemoglobin is
different to foetal haemoglobin so dissociation can occur
Haemoglobin
Transported in erythrocytes (red blood cells)
Associates with oxygen to form oxyhaemoglobin (Hb(CO₂)₄)
Consists of 4 polypeptide chains in a quaternary structure
Each chain consists of a non-protein haem group each containing an iron ion (Fe2+)
which attracts and holds oxygen molecules
Haemoglobin has a high affinity for oxygen
Oxygen dissociates and leaves haemoglobin to be released into respiring tissues
Partial Pressure of Oxygen
Oxygen tension = oxygen concentration
Also called partial pressure of oxygen (pO₂) and measured in kilopascals (kPa)
Oxygen has a long diffusion distance to the haem group
Low pO₂ = low saturation
After one O₂ molecule binds to a haem group, a conformational change occurs in the
haemoglobin molecule
The shape changes and the haem groups move to the outside
Allows O₂ molecules to associate with ease
Approaching 100% saturation, diffusion gradient decreases and oxygen struggles to
associate
After birth there is a change in environment to higher oxygen tension so adult haemoglobin is
different to foetal haemoglobin so dissociation can occur
