Chapter 1 



PHOTOSYNTHESIS AND ITS ROLE IN NATURE 



A. Organic Matter and Life Energy 



The chemical reactions which constitute the material aspect of life 

 all take place on a precariously high level of potential chemical energy. 

 Like acrobats performing their complicated exercises high above the 

 circus crowd, the molecules of proteins, carbohydrates, fats, vitamins, 

 enzymes, and other constituents of the living organisms combine, ex- 

 change, or dissociate in the midst of an ocean of oxygen which continu- 

 ously threatens them with breakdown and extinction. Oxygen atoms, 

 reluctantly united in diatomic molecules, are ever ready to break away 

 from each other and to seek stability' in the union with carbon, hydrogen, 

 phosphorus, iron or the other elements contained in organic matter. The 

 inorganic world has long since succumbed to a similar attack — so com- 

 pletely that now an average atom in the earth's crust is held in the grip 

 of two atoms of oxygen. Living matter, however, has escaped the same 

 fate by its remarkable capacity for regeneration. Every day, almost a 

 billion tons of organic compounds are destro,yed b}^ oxidation, finally to 

 pass into the air as carbon dioxide, or to return as water to the universal 

 moisture which surrounds and permeates all living things on the earth. 

 At this rate of destruction, all organic matter now present on this globe, 

 will be consumed in the next ten or twenty years; but during the same 

 period, an equal quantity of organic matter will be created, i. e., oxygen 

 will be expelled from its stable union with carbon and hydrogen, and the 

 liberated atoms knitted together into the intricate patterns which spell 

 the secrets of organic growth, propagation, heredity, sensitivity, and 

 mobility — all the properties which distinguish living organisms from 

 inanimate objects of the mineral world. 



Oxidation is, however, not merely a calamity, permanently threaten- 

 ing all living matter; it is also the prime mover of life. Life thrives on 

 death, not only because the material for organic synthesis comes from the 

 decay of living matter (if oxidation should cease, there would be no need 

 for this synthesis), but also, because oxidation is the main source of the 

 energy of life. Every movement of the animal body, every chemical 

 activity of the digestive system, every flash of thought in the brain, 

 consumes energy, and the main source of this energy is respiration, i. e., 



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