CHEMICAL KEACTIONS CAN BE INDUCED 243 



goes on slowly by itself, and gives out free energy, is actually 

 enormously increased in velocity 1 by another reaction which 

 absorbs energy in the process. The induced reaction runs the 

 inducing reaction backwards away from its equilibrium point by 

 means of the energy which would be otherwise set free. The 

 reason for the increased velocity is the same as in the case of 

 catalytic action; although free energy from the induced reaction 

 is taken up by the inducing reaction, the resistance in the process 

 of the intermediate stage due to setting free of nascent oxygen is 

 removed, and in this respect, although undergoing alteration itself 

 with absorption of energy, the metallic oxide acts as does a catalyst 

 in catalysed reactions. 



But it is in the metabolism of the living cell that we meet with 

 examples of such linked and induced reactions in greatest numbers. 

 Even in the animal cell, although the balance-sheet of metabolism 

 is in favour of oxidation with liberation of free energy, it is a mistake 

 to suppose that there are no reactions running in the reversed 

 direction. We have seen earlier, that with the varying conditions 

 of concentration in the cell the equilibrium point may alter so 

 that syntheses forming the reversals of simple hydrolytic cleavages 

 may readily occur in the cell, simply by the action of enzymes. 

 Such, for example, as maltose formation from glucose, of glycogen 

 formation from glucose, of protein from albumose, or even of 

 neutral fat from fatty acids and glycerine. Such syntheses demand 

 little or no energy, because the chemical energy of the substances 

 upon one side of the equation is practically identical with that of 

 the substances upon the other, and hence variations in osmotic 

 energy with changes in concentration may easily make the balance, 

 so that an enzyme which adds no energy may affect the conversion. 

 But in such cases of metabolic change as, for example, the conver- 

 sion of carbohydrates to fats, where, weight for weight, the energy 

 is almost double, or in the conversion of carbon dioxide and water 

 into organic compounds, as in the green leaf, where energy is also 

 taken up such energy must be provided from other sources and a 

 more complex mechanism than that of the enzyme, capable of linking 

 together different chemical reactions, or of acting as a transformer 

 of other energy forms into chemical energy, must be present. 



1 We cannot say catalysed, because the inducing substance does not 

 remain unaltered but takes up energy, but the difference is only in definition, 

 for, as far as chemical kinetics go, the action is virtually catalysed. 



