Explain the Bohr shift.

The Bohr shift should be explained using the relative affinities of haemoglobin to carbon dioxide and oxygen due to changes in pH level. When pCO2 is high in cells (i.e in muscle cells when one is exercising), the body urgently needs to remove the CO2 to avoid blood acidification. As CO2 decreases the pH of blood, the concentration of protons in the blood increases. These protons bind to haemoglobin molecules in erythrocytes and, as Haemoglobin is a protein, the proton binding causes a conformational shape change to the 3D structure. As a result of this shape change, Hb' affinity to oxygen decreases and instead has increased affinity for CO2 molecules, which are then carried in the blood stream to the lungs where the CO2 can be removed.