122 



PHOTOSYNTHESIS 



THE CHLOROPLAST REACTION IN RELATION TO 

 HYDROGEN TRANSPORT 



We have seen in Chapter 5 that van Niel suggested the 

 generahzation that the essential photochemical reaction in 



O 



100 



20 40 60 80 



Percentage reduction 



FIG. 7.2. Potentials and percentage reduction for substances con- 

 cerned with the chloroplast reaction. (After R. Hill.) i. 

 Oxygen; 2. ferricyanide; 3. cytochrome/; 4. quinone; 5. 2:6- 

 dichlorindophenol; 6. ferric oxalate; 7. hydrogen. 



all photosynthetic organisms is the 'splitting' of a water 

 molecule, the hydrogen being utilized for the reduction of 

 carbon dioxide whilst the oxidized radical produced either 

 breaks down with the liberation of oxygen as in the green 



