DANIEL I. ARNON 



555 



T23I-I 



30' L 



C|j , 5pM Ftm 



¥■ 



PHOSPHOGLYCERATE 



(^^ 



PHEHOL/ WATEH - 



Fig. 27. Radioautograph of a chromatogram showing products of photosynthetic 

 C"0„ assimilation by illuminated chloroplasts supplied with 0.5 microtnoles FMN 

 (Trebst, Losada, and Arnon, 151). 



Parallel experiments of Losada et al. (96) on specific enzyme sys- 

 tems in chloroplasts fortified these lines of evidence and supported 

 the conclusion that in a reconstituted "catalytic" chloroplast sys- 

 tem (in which COo assimilation can occur only in the light) , non- 

 cyclic photophosphorylation alone does not provide sufficient ATP 

 for a reductive assimilation of CO2 to the level of carbohydrate. 

 Additional ATP must be supplied by cyclic photophosphorylation. 



19. Photosynthesis and Biochemical Evolution 



The insight into the mechanism of photosynthesis gained from cell- 

 free experiments with chloroplasts and chromatophores permits us to 

 interpret, with somewhat enhanced confidence, certain aspects of 

 biochemical evolution which w^ have already discussed elsewhere 

 (18, 97) . 



