ELECTRON TRANSPORT IN R. RUBRUM 



301 



HYPOTHETICAL SCHEME ON PHOSPHORYLATING, 

 PHOTOSYNTHETIC ELECTRON TRANSPORT SYSTEM 



In summary, a hypothetical scheme for the electron transport sys- 

 tem in "intact" chromatophores of R. rubrum is presented (Fig, 21). 

 Under anaerobic conditions, electrons migrate through the electron 

 transport system in a cyclic fashion at the expense of the energy 

 absorbed from light in bacteriochlorophyll (BChl) and its accessory 

 pigment, carotenoids. The oxidation- reduction reactions around both 

 flavoprotein (FP) and cytochrome c 9 are able to couple phosphorylating 

 reactions. Differences in Eq between the excited bacteriochlorophyll 

 (around -0.32) and FP (0 to -0.2 V), and between cytochrome c^ 



1) In "young" cells: 



Excited BChl 



/ 



BChl 



ATP 



2) In "aged" cells: 



Oxidizable substances 



Oxidized products of BChl 



■hv 



Fig. 21. Hypothetical scheme for electron transport system in chromatophores 

 present in young or aged cells of light-grown 72. rubrum. 



