TRANSFERENCE OF FOOD MATERIALS 139 



reserves. When required the reserves are hydrolysed and 

 used as simple substances. These changes are due to the 

 reversible action of enzymes as shown hi the following diagram : 



Food reserves by enzyme For transference or oxidation 



Polysaccharides Z^ Monosaccharides 



Fats ___>. Glycerine and fatty acids 



Proteins __>. Ammo acids. 



The importance of the simpler substances in cells has been 

 emphasised by Hopkins, who pointed out that chemical 

 changes hi cells are mainly concerned with the simpler sub- 

 stances, whilst the larger complex molecules are of more 

 importance from the physical aspects of cell activities.* 



Therefore the digestive processes elaborated in this and the 

 preceding chapter are of much wider significance than the 

 mere process of digestion in mammals. Transfer of food 

 materials in plants and the chemical changes in individual 

 cells all depend on reversible hydrolysis of the stored colloidal 

 and insoluble food reserves. 



GENERAL REFERENCE 

 I. MUNK : Ergeb. der PhysioL, 1902, vol. i, part I, pp. 296-329. 



* F. G. Hopkins, Brit. Ass. Reports, 1913, p. 652. 



