54 Life: Its Nature and Origin 



synthesis would have occurred in the cell. In other words, of the 

 great procession of syntheses which make up the chain of growth 

 in a modern cell, only the last two or three steps would have oc- 

 curred in the primeval cell. These authors believed that during the 

 evolutionary process more and more of these syntheses became 

 incorporated in the cell itself in an orderly fashion starting back- 

 ward from the point at which synthesis began inside the parent 

 cell. According to this view there is some basis for speculating 

 that the nuclear membrane (Fig. 19) may represent the primeval 

 cell membrane and that the cytoplasm represents all the molecular 

 machines which have been added subsequently and then invested 

 with a second membrane of their own during the course of evolu- 

 tion. The evolutionary mechanics adding a whole "outside layer" 

 are, however, difficult to visualize. 



That new processes, or molecular machines, have been added to 

 the cell seems certain. One of the most important was the process 

 of photosynthesis, by which carbon dioxide and water are con- 

 verted to carbohydrate with the liberation of oxygen. This addition 

 provided a new source of food for life and changed the atmosphere 

 to an oxidizing one, thus creating new environmental conditions 

 affecting the process of natural selection. 



A second important development probably followed the evolu- 

 tion of photosynthesis. Most authors agree that the early organisms 

 obtained energy by the chemical process of fermentation. In this 

 process only a small amount of the chemical-bond energy is ex- 

 tracted from sugar, but without using free oxygen it is as far as an 

 organism can carry the energy-extracting process. After the advent 

 of photosynthesis, oxygen was added to the atmosphere and aquatic 

 medium. In some organism an enzyme system evolved which was 

 able to utilize the oxygen in oxidizing sugars down to their ultimate 

 compounds, CO2 and H2O, and to utilize this added energy for 

 activating livirg processes. This oxidation process, called respira- 

 tion, releases 30 times as much energy as fermentation from a 

 given quantity of sugar. 



Mechanics of respiration in living organisms indicate that respira- 

 tion was added to an original fermentation process which is still 

 the first step in energy production in protoplasm. Indeed, present- 

 day cells may lose their oxidative machinery and still exist at a 

 reduced tempo on their fermentation facihties alone. Dramatic 

 demonstration of this ability was given by Warburg (1956), who 

 showed that cancer cells are simply normal cells damaged to a 

 critical point at which respiration (oxidation) is stopped, but at 



