WP 



Other 

 biosynthetic 



^^^ products 



As we learn more about the capabilities of the chloro- 

 plast to form compounds from carbon during photosynthesis, 

 we come closer to the conclusion that the chloroplast, as it 

 exists in the living, undisturbed cell, is a self-sufficient factory 

 capable of producing essentially all the materials required 

 for its replenishment. Thus it appears to be able to make 

 all kinds of sugars, polysaccharides, protein, fats, pigments, 

 enzymes, and cofactors. In addition to this, it produces for 

 export to the cytoplasm reserves of organic compoimds. 

 These are probably sugars, glycolic acid, and other neutral, 

 relatively small, molecules which can be readily transported 

 through the chloroplast membrane. Until more is known 

 about the development and formation of chloroplasts, we can- 

 not say just when it gains this complete synthetic ability. No 

 doubt there are early stages in the development of chloro- 

 plasts in which it must be built from cytoplasmic materials 

 derived in turn from already-functioning chloroplasts. There 

 is no reason to suppose the chloroplast functions without nu- 

 clear control, even though it does not appear to have a nu- 

 cleus of its own. Presumably it is possible for RNA mole- 

 cules to move in and out of the chloroplast in some way. It 



67 



