140 CHEMICAL TRANSFORMATIONS IN 



is seen in the cell differs from the simpler inorganic catalysts and 

 the enzymes formed by cells. As a rule, the simpler enzymes 

 are only capable of inducing reactions in which no substances are 

 formed with larger storage of chemical energy. But the cell is 

 able from a supply of substance, such, say, as soluble carbohydrate, 

 to oxidise part to yield energy, and utilise this energy to build up a 

 smaller amount of a substance, such as a fat, possessing for an equal 

 weight a higher amount of chemical energy. 



The fluids with which the cells are bathed and which permeate 

 them may be regarded as solutions containing, in a few common 

 forms supplied universally to all the cells, energy in a chemical 

 form which is utilised by the cells to carry on their reactions. 



Depending upon the type of the cell and the enzymes which it 

 contains, varying reactions are induced in this common medium, 

 so that different products are formed, and different amounts and 

 types of energy set free. 



In following out the energy exchanges it is hence necessary to 

 consider the properties of solutions, such as the velocity of reaction 

 and the conditions of equilibrium between the reacting substances ; 

 the forms in which energy is present and the amount of change in 

 energy as the substances react; and how the presence of catalysts 

 alters the energy exchanges in the solution. 



The law of conservation of energy teaches that the total amount 

 of energy must remain the same, and hence the algebraic sum of 

 the amounts of energy changing from one form to another must 

 be equal to zero. 



Since we possess no means of stating the absolute amount of 

 energy contained by a system in any of the varied forms in which 

 energy manifests itself, we can only estimate the change of energy 

 in any given form as the system passes from one condition to 

 another, and to obtain the total change in the system the amount 

 of change in each particular form of energy undergoing change 

 must be taken into account. The amount of change in each form 

 of energy is obtained from the product of the capacity factor of 

 the system for any particular form of energy, and the change in 

 the potential factor of that form of energy. 



In the case of certain forms of energy the capacity and potential 

 factors are still unknown to us, and the amount of energy taken up 

 or given out in these forms during a change of energy from one given 

 form to another can only be estimated by a statement of corre- 



