110 



TEST-TUBE ENERGY 



Another development comes from 

 an cnzjniologist, Efraim Racker, of the 

 Public Health Research Institute of 

 the City of New York. Dr. Racker, in 

 a communication to Nature (February 

 5, 1955) reports the production of 

 sugar by purely chemical interactions. 

 What he did was to crush spinach 

 leaves, separate and discard the cellular 

 fragments, and extract an aqueous solu- 

 tion containing a concentrate of the 

 natural synthesizing enzymes of the 

 plant cells. To this solution he added 

 carbon dioxide, put in certain energy- 

 rich phosphate compounds to supply 

 the cnerg^', bubbled hydrogen gas 

 through tiie mixture to supplv the 

 necessary hydrogen, and added a spe- 

 cial enzyme which facilitates the use of 

 molecular hydrogen. There was no 

 need of light, since the phosphate 

 compounds supplied the energ\^; and 

 for the same reason there was no need 

 of chlorophyll. 



PHYSIOLOGY 



Thus, by a cycle of reactions that 

 were strictly chemical, promoted at 

 each step by the appropriate catalyzing 

 enzyme, Racker produced glucose sugar 

 in a test tube. Tlie value of this work is 

 its demonstration of the exclusively 

 chemical nature of the carbon-dioxide 

 reducing system— the dark phase of 

 photosynthesis which takes the h\dro- 

 gcn and the elements of the carbon 

 dioxide and builds them into the en- 

 erg^'-packed structure which is sugar. 



So the first steps seem to have been 

 taken, their direction is fonvard, and 

 Szent-Gyorg\'i's dream of a benevolent 

 "chlorophyll bomb" may not be so 

 Utopian after all. Transferred to the 

 chemist's vats and tanks, isolated from 

 the distracting milieu of the living cell, 

 the processes of photosynthesis should 

 become more manageable, the gaps in 

 our knowledge of its ways be more 

 surely bridged— hastening the day 

 when the world's production of food 

 will catch up with the needs of the 

 world's hungry. 



QUESTIONS 



1. What is meant by the phrase "Our 

 Bridge from the Sun"? 



2. Wliy is sugar so important to the or- 

 ganic world? 



3. Mention briefly the contributions of 

 Priesdey, Ingcn-Housz, Senebier, de 

 Saussure, von Majer, van Niel, Black- 

 man, Calvin, Hill, Arnon, and Racker 



to the solving of the riddle of photo- 

 synthesis. 



4. The following compounds are involved 

 in photosynthesis. Place them in the 

 correct order of formation, as far as is 

 known: PGA, Triose, RuDP, Glucose. 



5. What connection might there be be- 

 tween the world population crisis and 

 photosynthesis? 



