METABOLISM 



127 



Corbon Dioxide 



Water 



Process of Pho1"OSunthcsis 



f(^)mmmmm(c) — > 



I ^ — ^ 



Process of Respiraiion 



^ 



I ^ 



Fig. 67. — The energy relations of photosynthesis and respiration. Diagram 

 showing the operation of a simple laboratory model. A, six molecules of carbon 

 dioxide and six of water, the raw materials for photosynthesis. B, photosynthe- 

 sis. By the kinetic energy of light, the molecules of carbon dioxide are broken 

 up and the carbon atoms are being pulled over and attached to the water mole- 

 cules, thus stretching the six springs which unite the carbon and oxygen. C, the 

 products of photosynthesis, a molecule of glucose and six of oxygen. The energy 

 exerted in photosynthesis is now stored in potential form in the glucose molecule 

 (actually, of course, in the stretched si^rings). D, respiration. The potential 

 energy in glucose is being released in kinetic form (by the contraction of the 

 springs) in respiration, as the result of which the atoms are again arranged as six 

 molecules of carbon dioxide and six of water. This, of course, is a very crude 

 imitation of the processes involved and should not be interpreted too literally. 



