298 



UNITY AND DIVERSITY IN BIOCHEMISTRY 



"Bohr effect". This influence of changes in the Pqq^ is due to changes in 

 the pH causing changes in the dissociation of the amphoteric haemoglobin 

 and thus ahering the properties of the oxygen -binding groups. When the 

 Pqq^ of an alkaline solution of haemoglobin is increased, the pH approaches 



100 



Fig. 86 (Morgan and Chichester) — Dissociation curves of haemoglobins of man, 



dog and pig. 



the isoelectric point of the carrier and the dissociation of its acidic groups 

 diminishes. The affinity of haemoglobin for oxygen diminishes likewise 

 and the p^o value increases since the dissociation curve is displaced to the 

 right. Figure 88 illustrates this phenomenon for horse haemoglobin. 

 Since the influence and extent of the Bohr effect is very variable, to compare 

 the oxygen affinities of different haemoglobins it is necessary to compare 



