cannot be said at the moment whether or not the chloroplast 

 is capable of synthesizing nuclear material. It would seem 

 likely, however, that the chloroplast can synthesize pu- 

 rines and pyrimidines, coenzymes, and nucleotide materials 

 needed for the continued functioning of the chloroplast as 

 a self-sufficient biosynthetic factory. If, as we now think, 

 protein synthesis and enzyme synthesis occur in the chloro- 

 plast, then either the chloroplast must obtain a store of RNA 

 molecules at its initial construction or else such molecules 

 must be able to travel back and forth from the chloroplast 

 to the cytoplasm. 



In conclusion, we should say that the point of view of 

 the ability of the chloroplast to carry out photosynthetic 

 formation of many compounds is a departure from the view 

 held only a few years ago. It was then thought that the primary 

 function of photosynthesis was to form carbohydrate only. 

 This carbohydrate was then thought to be used by the cyto- 

 plasm in the synthesis of all other compounds. Of course, the 

 chloroplast must stipply the carbohydrate and reducing power 

 for the cytoplasmic synthesis. It now appears that chloroplasts 

 also synthesize a complete spectrum of biochemical products, 

 all of which might reasonably be considered to be photosyn- 

 thetic products. Finally, as we learn more about the photo- 

 synthetic paths to these products, we are impressed not 

 merely by their complexity but much more by the economy 

 with which both energy and material are utilized. 



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