[Chap. XIV 



THE RATE OF PHOTOSYNTHESIS 



125 



of picturing what has just been said, one of the recent suggestions may 

 be outlined as follows: 



Light energy + Chlorophyll + CO2 + H2O > Chlorophyll carbonate 



Chlorophyll carbonate + Enzyme + HoO > Sugar + Free oxygen 



In the process the chlorophyll and enzyme have been converted to their 

 original states. 



The process is undoubtedly more complex than is indicated here. The 

 difficulty of arriving at scientifically established answers to many ques- 

 tions about biological processes lies partly in the complexity of the trans- 

 formations that proceed as a chain of reactions, and parth' in the com- 



HC=CH, 



H 



H3C— C / 



\/^\/X 



- — ^ / "^ 



^ \ / \ 



iCH,) (HC=0l 



/ 



)^^ JZ C2H5 



HC 



H3C— c^, \ 



>" \ 



// C CH3 



I 



CH. 

 I ' 

 CH 



I ^ 



c=o 



COOCH 



COOC20H39 



Fig. 56. Diagram representing the arrangement and complexity of the molecule 

 of chlorophyll a. If the group, CHO, in the detached circle is substituted for the 

 CH3 group nearby, the diagram would represent the molecule of chlorophyll b. 

 From B. S. Meyer and D. B. Anderson, 1939. 



plexity of the large molecules involved in the reactions. The empirical 

 formulas of the two chlorophylls, a and b, are given on page 28. Merely 

 to illustrate the complexity of these compounds, one of the recently pro- 

 posed structural formulas for chlorophyll is reproduced here ( Fig. 56 ) . 

 Before we can know exactly how photosynthesis occurs, it will be 



