RESPIRATION 



469 



transformation first into gluconate and then into 2-oxoglucon- 

 ate. However, these products are later phosphorylated and 

 transformed with the formation of numerous compounds, in 

 particular 5- and 7-carbon sugars (ribose and sedoheptulose). 



GLUCOSE — 



I 

 I 



i 

 GLUCOSE-6-PO4 



-2H 



^ GLUCONATE 

 + ATP 



-2H 



-2H 



6-po4-6luconate 

 -2h/h:o, 



^ 2-KETOGLUCONATE 



+ ATP 



2-KET0-6-PQ,- 

 GLUCONATE 



FRUCTOSE-6-P0, 



SEDOHEPTULOSE - 

 , 7-PO4 



?— , 



>' ^, 



'4 

 ♦ ATP 



GLYCERALDEHYDE- 

 ..< 3-PO4 



->- PYRUVATE 



^■ 



FRUCTOSE-1,6- 

 di-P04 



Fig. 41. Pathways in glucose oxidation by 



Pse udo m o nas flu o rescens 



(after Wood).!^^ 



But the old metabolic pathway is retained in Pseudomonas 

 fluorescens and, under certain conditions, this organism can 

 transform sugar via glucose-6-phosphate, fructose-6-phosphate 

 and fructose diphosphate. 



In his communication to the Third International Congress 

 of Biochemistry in Brussels, F. Dickens^^^ gave the following 

 scheme for the interaction of the glycolytic and oxidative 

 mechanisms in metabolism (Fig. 42). 



This diagram shoAvs where the Krebs cycle is incorporated 

 in the glycolytic mechanism and also the connection between 

 this mechanism and the direct oxidative degradation of 

 glucose. This scheme was worked out for the most part with 

 the animal cell, but Dickens considers that it is also valid 

 for yeast. Furthermore, the fact that the appropriate sugars 

 and enzymes are also found in higher plants (Calvin) suggests 

 that the mechanism also operates in these organisms. 



Thus, although the first system of reactions taking part 

 in respiration varies considerably among the more primitive 



