386 THE FIRST ORGANISMS 



immediate and decisive effect on the entry of substances into 

 the cell. 



In an analogous way the characteristic features of cellular 

 energetics depend on the high degree of organisation of the 

 metabolism of protoplasm.^" In the engines which are widely 

 used in industrial processes, the chemical energy which is 

 liberated by burning the fuel is usually first converted into 

 heat and only later transformed into other forms of energy. 

 In protoplasm the energy liberated by the decomposition of 

 organic substances (in the process of fermentation or by their 

 oxidation during respiration) is converted directly into the 

 forms of energy required for life. Owing to this an extremely 

 high coefficient of utilisation of energy is achieved in living 

 bodies such as is not approached by our technology. In the 

 engines of the present time this coefficient reaches, at best, 

 40 per cent, and this requires considerable temperature 

 differences, of the order of hundreds of degrees. If the trans- 

 formation took place in living bodies in the same way as in 

 heat engines, then, at the temperature differences which are 

 possible for organisms, the coefficient of energy utilisation 

 would only be a fraction of 1 per cent. Nevertheless it in fact 

 reaches 50 per cent or even more. This is explained by the 

 fact that the breakdown and oxidation of sugar or other 

 energy-yielding material does not take place as an isolated 

 process in the living cell, but through a series of separate 

 reactions which are strictly co-ordinated in time and which 

 form the chains and cycles which constitute metabolism. The 

 chain of alcoholic fermentation and the oxidative cycle of 

 Krebs may serve as examples. 



It must be pointed out that if the oxidation of organic mole- 

 cules were to take place all at once in protoplasm, the living 

 body would not be able to make rational use of the energy 

 thus liberated. The oxidation of only one gram-molecule of 

 sugar to carbonic acid and water liberates about 700 kcal. 

 The instantaneous release of this amount of energy would 

 be associated with a sharp rise of temperature, the denatura- 

 tion of proteins and the destruction of protoplasm. The 

 energetic effect achieved by protoplasm at ordinary low tem- 

 peratures depends on the fact that, in the process of biological 



