<p>When bound to oxygen it is referred to as oxyhaemoglobin and when unbound, deoxyhaemoglobin. Haem gives blood its colour, and this colour depends on its saturation. When fully saturated with four oxygen molecules it appears red and when completely unsaturated it appears blue-red.</p> | <p>When bound to oxygen it is referred to as oxyhaemoglobin and when unbound, deoxyhaemoglobin. Haem gives blood its colour, and this colour depends on its saturation. When fully saturated with four oxygen molecules it appears red and when completely unsaturated it appears blue-red.</p> |