THE CHEMISTRY OF PHOTOSYNTHESIS 161 



CO2 removed by NaF must be linked in some way or other with chlorophyll. 



If the NaF concentrations are varied, the end values remain the same but 

 the lower the NaF concentration, the slower the rate of CO2 removal. The 

 COo removal by NaF is not a simple reaction. It is inhibited by small 

 amounts of HCN and by heating for 5 min at 65 ° C. Thus, it seems that 

 NaF does not have a direct action. Its addition starts an enzyme reaction 

 responsible for the COo removal by means of a heavy metal compound. The 

 addition of phenanthroline does not inhibit the action of NaF, so that the 

 enzyme does not seem to be a dissociating heavy metal compound (see § 31). 

 As phenylurethane does not influence the CO2 removal, it may be concluded 

 that the enzyme is not structure bound. 



The fluoride reaction is reversible if the concentration of NaF is not too 

 high. When the NaF is washed out after CO2 removal, the cells are again 

 able to take up CO2. This renewed uptake is only possible in the presence of 

 O2. Therefore, the binding of labile CO2 in the cells is not a reaction by itself 

 but needs respiration, i.e., energy. 



Warburg and Krippahl (15) established that the addition of a drop of octa- 

 nol to Chlorella removes 1 mole CO2 from 1 mole chlorophyll. This CO2 re- 

 moval is irreversible because of the cytolytic properties of octanol. It fol- 

 lows from this that chlorophyll isolated by means of organic solvents does not 

 contain labile CO2. As a matter of fact, there is no place for CO2 in the chlo- 

 rophyll formula. We must therefore distinguish between isolated and func- 

 tional chlorophyll, i.e., between "dead" and "living" chlorophyll (see § 2). 



Numerical example (15): 



Vessel I: I',- = 3.2 ml V,, = 15.48 ml A'co, = 1.725 mm- 



Vessel II: Vp = 3.2 ml \\, = 15.53 ml /Ceo, = 1.732 mm^ 



Per vessel 200 n\ cells in 3.0 ml salt solution, pH 3.8. Chlorophyll content 7.7%, 

 i.e., at 22.5% dry weight: 3.83 /xmole. In the side-arm of vessel I: 0.2 ml H2O. 

 In the side-arm of vessel II: 0.2 ml 0.2 .YNaF (pH 3.8). Gasphase: argon. Ex- 

 periment carried out in the dark. Temperature: 20° C. 



Vessel I Vessel II 



Pressure Changes Pressure Changes 



After Tipping After Tipping 



+ 0.5 mm +32.0 mm 



mm +11.5 mm 



+ 1.0 mm + 7.0 mm 



+ 0.5 mm + 1.0 mm 



+ 1.0 mm + 1.5 mm 

 + 0. 5 mm mm 



45 min +3.5 mm +53.0 mm 



Vessel I: xco, = 3.5 X 1.725 - 6.0 yul. Vessel II: xco, = 53.0 X 1.732 = 91.8 Mi- 

 Labile CO2: 91.8 - 6.0 = 85.8 n\ = 3.86 /imole 



labile CO2 in ^mole _ 3.86 _ 

 chlorophyll in jumole 3.83 



