CELLULAR METABOLISM I29 



follow membrane formation and end in cell division constitute the 

 aerobic phase and must require the energy provided by oxidative reac- 

 tions. The increased utilization of glycogen accompanied by the in- 

 creased utilization of pyruvate (Table X) may provide the energy nec- 



TABLE X 

 Utilization of Pyruvate by Arbacia Eggs — Influence of Fertilization. 



essary for the process of cell division (32). Furthermore, the intro- 

 duction during the cell division process of three of four oxidative steps 

 (the series of oxidations carried on by the cytochrome system) in the 

 series of reactions from substrate to molecular oxygen will increase the 

 efficiency of the reactions so that for the same amount of O2 utilized 

 there will be a more efficient utilization of energy. Whether carbo- 

 hydrate is metabolized entirely via glycolysis, or is oxidized through 

 the pathway of hexosemonophosphate oxidation as suggested by Or- 

 strom and Lindberg (70) is not known. Neither is the nature of the 

 acid formed on cell division known. Some of it may be acetic acid 

 formed on oxidation of pyruvic acid. Whether acetate is utilized or not 

 is not known. If it is, the pathway of its oxidation must be different 

 from that of most animal tissues because neither succinate nor a-keto- 



