THE PHOTOTROPHIC ASSIMILATION OF CARBON 43 



Labelled amino-acids appear at an early stage when algae 

 photosynthesize in the presence of radioactive carbon 

 dioxide. Radioactivity appears first in aspartic acid, alanine, 

 serine and glycine among amino-acids.^^ Aspartic acid and 



in 



<-^ 



J 

 O 

 ffl 

 < 



ACID METABOLISM 



r 



TCO5 



■^ 



±NH3 



CITRATE 



ra-KETOGLUTARATE :^ 

 -CO, 



•HIGHER FATTY 



ACIDS 



N 



:iGLUTAMATE , 



NH3 



SUCCINATE 



MALATE 



GLUTAMINE 



ASPARAGINE 



k 



TNH3 



±NH3 

 OXALO ACETATE ^ *" ASPARTATE- 



+ CO. 



GLYCEROL 



C0« 



±NH3 

 PYRUVATE ^, '' ALANINE 



N 



TRIOSE 



phosphates' 



HEXOSE 

 PHOSPHATES 



— PHOSPHOGLYCERATE GLYCINE 



\ 



+ CO2 



+ NH, 



C2 ACCEPTOR >-GLYCOLLATE 



L f 



PHOTOSYNTHESIS ^ 



O 



PI 

 > 



O 



r 



Fig. 10. Scheme showing the inter-relationships between photo- 

 synthesis and acid, carbohydrate, fat and protein metaboHsm. 

 For the sake of clarity many intermediate reactions have 

 been omitted. 



alanine arise by the addition of the -NHg group to oxalo- 

 acetic and pyruvic acids respectively. Serine may perhaps 

 be derived from pyruvic acid and, as mentioned above, 



