- Haemoglobin has the structure of 4 polypeptide chains interlinked with a haem group containing iron, this allows for oxygen transportation- each haemoglobin molecule can carry 4 oxygen molecules.
- Haemoglobin must not only pickup oxygen at the lungs but drop it off at the appropriate tissues. This is known as dissociation, and it is possible to measure haemoglobins dissociation and produce a graph, known as a dissociation curve
High affinity for oxygen- oxygen is easily taken up but is less readily released.
Low affinity for oxygen- oxygen is less easily taken up but is released easier.
The Bohr Effect
The Bohr effect is the influence of carbon dioxide on the S-shaped graph - when carbon dioxide is released into the red blood cells, it is converted an enzyme carbonic anhydrase, which produces excess hydrogen ions as a result. Haemoglobin readily combines with these ions, forming haemoglobinic acid, and in doing so releases the oxygen which it is carrying.
This results in two things - haemoglobin intaking the hydrogen ions which are formed when carbon dioxide dissolves and dissociates - keeping the pH neutral (acting as a buffer).The fact that a high partial pressure of carbon dioxide causes haemoglobin to release oxygen - this is the Bohr effect. It is very useful in that high concentrations of carbon dioxide are found in actively respiring tissues - the ones that need oxygen the most, and cause haemoglobin to release oxygen even more readily that it would otherwise do. The Bohr Effect shifts the S curve slightly to the right.