A haemoglobin molecule can 'bend' between two slightly different shapes known as the 'tense' and 'relaxed' conformations - shown on the left and right above respectively. The important point here is that the relaxed conformation can bind oxygen more easily.
Several factors will determine which shape a haemoglobin molecule takes, such as the pH, temperature and PCO2 of its surroundings.
How much oxygen it has bound to it will also affect its shape, the more oxygen bound to it, the more it takes on the relaxed conformation and so the more easily it will bind more oxygen. This effect is what causes the shape of the oxyhaemoglobin dissociation curve - more on this later.
Image by BerserkerBen from Wikipedia under licence https://creativecommons.org/licenses/by-sa/3.0/ and split from the animated gif into two images.
No comments:
Post a Comment