SALT ABSORPTION AND METABOLISM 



79 



Reduction 



MEMBRANE 

 (d) 



Fig. 28 (c-d). The LundegSrclh hypothesis, 

 c. Diagrammatic representation of the Lundegardh hypothesis. (For ex- 

 planation see text); d. Anion transport involving a chain of cytochrome 



molecules. 



on the inside. The gradient might depend on differences of oxygen 

 pressure on the two sides, or on the spatial location of enzymes. 

 Cytochrome is presumed either to be freely diffusible within the 

 membrane or to vibrate from one position to another, so that it 

 becomes alternately oxidized and reduced. Anions are taken up 

 when cytochrome becomes oxidized at the outer surface and released, 

 when it becomes reduced at the inner surface because of the ability' 

 of an oxidized cytochrome molecule to bind one more anion than 

 can a reduced molecule. Transport of anions across thin membranes 



