44 VELOCITY OF REACTION, AND 



cells, and notably in the anabolic processes of chlorophyll-con- 

 taining cells of living plants, why does the reaction proceed away 

 from the equilibrium point with storage of chemical energy, instead 

 of energy being set free ? 



There is ho shadow of doubt as to the experimental facts which 

 suggest these queries, all of which form a connected whole, and 

 must receive their explanation on a common basis. 



Sterilised solutions of cane-sugar, maltose, lactose, and starch 

 can be preserved indefinitely without any measurable change 

 into their simpler components. On the other hand, solutions in 

 molecular proportions of the constituent hexoses which build up 

 these more complex carbohydrates can similarly be kept in solu- 

 tion with no observable change for indefinite periods. There is 

 hence no movement towards the equilibrium point from either 

 side of that point. But let the appropriate catalyst be added 

 under the proper conditions and at once the reaction towards 

 equilibrium occurs. 



Still more striking are the examples derived from the metabolism 

 of living cells. 



Carbon dioxide and water or water vapour may be left together 

 indefinitely at such temperatures and physical conditions as obtain 

 in the chlorophyll- containing cells, and no formation of organic 

 compounds occurs. Similarly, the organic compounds produced 

 can be left under like conditions, and no chemical changes are 

 observed. But in the green plant cell, under the influence of 

 the solar energy movement directly away from the equilibrium 

 point of undirected chemical and osmotic energy takes place, 

 and gives the origin to the whole system of vital processes on the 

 planet. 



The fundamental groundwork for an answer to the queries 

 has been outlined in the introd action to this chapter. For energy 

 exchanges to occur it is necessary that there should be present the 

 properly adapted machines or energy -transformers. It is not 

 sufficient that there should be differences in energy potentials in 

 the system in order that a reaction may occur ; these give but the 

 possibility for the reaction, which can never take place unless in 

 addition conditions are present which allow the transference between 

 the forms of energy possessing differences in potential. 



The equations with which we have been dealing under the 

 heading of chemical equilibrium teach us, that at other positions 



