

Fats 



During photosynthesis by unicellular algae, it is not 

 uncommon for as much as 30 per cent of the carbon dioxide 

 taken up to be incorporated into fats. In Scenedesmus, for 

 example, after 5 minutes in light in the presence of C'*- 

 labeled carbon dioxide, 30 per cent of the fixed radioactivity 

 is found in lipid materials. This incorporation of radiocarbon 

 is greatly in excess of the rate of any synthesis that could 

 take place in the dark and is an indication of the stimulation 

 of fat production in the light. Fat synthesis requires a greater 

 number of equivalents of reducing agents than does synthesis 

 of carbohydrate or protein. Moreover, the composition of 

 the chloroplasts includes a very high proportion of fat ma- 

 terial. Since there is an abundance of reduced cofactors and 

 ATP in the chloroplast, and since the end product, fat, is 

 needed in the chloroplast, it is likely that much fat synthesis 

 takes place in the chloroplast and is therefore to be consid- 

 ered photosynthetic. 



Fatty acids 



All the well-known biosynthetic pathways to fatty acids 

 require as a starting material acetate or acetyl CoA. We have 



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