426 



Birgit Vennesland 



CVI 



O 



4. 



10 20 30 



Minutes 



OJ 



O 



80 



1 1 r~ 



Dried Soneroted Chlorella 

 With TPN (Argon) 



2% CO2 



Soneroted Chlorella With 

 TPN (Argon) 



2% CO2 



20 40 60 



Minutes 



Fig. 2 Effect of CO on Photoreduction of TPN 



(9) 

 Krippohl have recently published . The upper part of the graph shows a 



similar set of measurements made with soneroted Chlorella extract which had 

 first been lyophilized. Soneroted Chlorella extract contains all of the pro- 

 teins necessary for TPN photoreduction. Since the necessary soluble com- 

 ponents hove not been removed, it isn't necessary to odd them. It is also 

 unnecessary to use any special procedures to remove the CO„. 



The question of the energetics of TPN reduction is an interesting one. 

 There is insufficient energy In one photon of red light to effect a reduction 

 of two molecules of TPN with release of one molecule of O^. If the re- 

 duced carbon generated by 0„ elimination is completely reoxidized by 

 TPN, then some of this reduced TPN must be reoxidized by part of the 0„ 

 in order to achieve an adequate energy balance for the net reduction. With 

 soneroted Chlorella extracts, Warburg and Krippohl have demonstrated that 

 there Is a re-reduction of 0_ occurring during the Hill reaction with TPN. 

 Addition of HCN to Inhibit cotolase results in an inhibition of 0„ evolution, 

 and on accumulation of H^O^''^/. There is on apparent shift from an ordl- 



.22 . ■ 

 nary Hill reaction too dlsmufatlon: 



TPN + 2 H2O 



■^ TPNH2 + H2O2 



This dismutation occurs under on atmosphere of argon. The 0„ necessary 

 for H„0„ formation must come from the 0„ evolved in the inlriol Hill 



