DERIVATION AND CONVERSIONS OF ENERGY 251 



cent. This is converted and stored as potential energy in photo- 

 synthesis, which is a reducing process, oxygen being set free. 

 The material thus formed is carried to all parts of the body and 

 furnishes energy for growth, morphological construction, move- 

 ment, and maintenance of the rigidity and position of the body. 



Translocations of the compounds allows energy to be liberated 

 in the particular cells in which it is needed. During the libera- 

 tion of potential energy by physiological combustion some of it is 

 converted into kinetic forms such as heat, which is but of little use 

 to the plant and so is lost. 



Two principal types of liberation of energy may be designated 

 as aerobic and anaerobic respiration. Aerobic respiration con- 

 sists in the oxidation of the complex compounds of living matter, 

 or of the substances which saturate the meshwork, in a manner 

 which if completely carried out results in the formation of water 

 and carbon dioxide. The combustion may proceed only so far 

 as to produce organic acids however, and may not be accom- 

 panied by any excretion or formation of carbon dioxide. 



Anaerobic respiration (often termed intramolecular respiration) 

 is the process by which disintegration and liberation of energy, in 

 compounds in the cell, are produced without the aid of oxygen. 

 Sugar and proteids may be broken up in anaerobic respiration 

 producing carbon dioxide, water, sometimes hydrogen, nitrogen, 

 ammonia, amido- acids, and most generally alcohols. In one 

 form of anaerobic respiration special substances known as enzymes 

 are secreted by protoplasm which produce decomposition of 

 various compounds by fermentative action, or such action may be 

 exercised directly upon compounds in its meshwork (See 

 oxidases). It is to be noted however, that not all fermentative 

 processes are respiratory, since some of them are purely digestive 

 in their purpose. All of the above methods of liberation of energy 

 may proceed side by side, and the various steps in the separate 

 processes are not well known. 



Respiration goes on continuously in all organisms, but is re- 

 duced to a minimum in living plants in a desiccated condition, 



