330 



RADIATION BIOLOGY 



carbon dioxide was present, he saw no difference in the stationary level 

 in light and darkness. 



The role of the phosphate compounds in photosynthesis is not very 

 clear from an energy point of view. Even if 10 quanta is allowed for 

 the reduction of one molecule of carbon dioxide (see Chap. 4), in case of 

 exclusive generation of phosphate bonds only about 120 kcal/mole would 

 be available for the reactive systems, from which 112 kcal would have 

 to be fixed as CH2O. Even if the formation of two high-energy phos- 



26 



24 



2 2 



qT 2 



1 2 3 4 5 6 



TIME, hr 

 Fig. 5-18. Changes in trichloroacetic acid-sokible phosphate in suspensions of 

 Chlorella in the presence or absence of CO2 (pH ^ 4.0, 25°C). | Hght on; [ light 

 off. {From Wassink et al., 1951.) 



phate bonds per quantum were accepted, the space for energy losses 

 would not be too large, especially since some authors accept a lower 

 quantum number (see, for example, Kok, 1948; Warburg et al., 1950). 

 Recently Wassink (1951c) suggested that in connection with the phos- 

 phate cycle an active form of hydrogen might also be generated.'' A 

 similar view is discussed in some more detail by Kandler (1950), with 

 some interesting estimations of energy. Recently Holzer (1951) pro- 

 posed a scheme of photosynthesis in which a role was attributed to ATP. 

 The evidence so far obtained shows that at least the transfer of light 

 energy [system (2), Sect. 2] is intimately connected with phosphate 

 conversions. 



5. SOME REMARKS ON ENERGY TRANSFER IN PHOTOSYNTHESIS 

 In this section a few remarks on energy transfer may be added. This 

 may be considered as a discussion of part of process (2), given in Sect. 2. 



^ This view was expressed at a Symposium for Biokatalysis at Utrecht, Feb. 2, 1951. 

 Professor E. Havinga, Leiden, then suggested the following possibility [cf. Wassink 

 (1951c), p. 977]: 



H H 



/ hv 



RCH, 



-C— H 



\ 

 0- 



O + X 

 -P— OH 



RCH=C 



O' 



O 



^P— OH + XH2. 



OH 



OH 



