102 V filOLO&ICAL CHEMISTRY 



of oilier forms of -energy. Some organisms can oxidise 

 organic or inorganic substances and use the energy so derived 

 for the reduction of carbon dioxide. This is called chemo- 

 synthesis. 



Most leaves deposit the carbohydrate in the form of starch. 

 The deposit usually occurs in concentric layers in the small 

 oval bodies like those which contain the chlorophyll (plastids). 

 The starch is relatively insoluble, hence it is deposited as soon 

 as a small amount is formed. As this deposit gives rise to a new 

 phase the concentration of starch in solution can never rise 

 above the minute amount in equilibrium with the solid starch. 

 Therefore, as the concentration of starch remains low the 

 concentration of sugar remains low, and the condensation 

 of formaldehyde is not inhibited by the accumulation of sugar 

 in solution. On the other hand, removal of sugar will cause 

 the starch to be hydrolysed to sugar, and as the starch in 

 solution disappears more must dissolve to maintain equili- 

 brium, hence the starch granules dissolve and are used by 

 the cells. 



This outline indicates the usual principle involved in the 

 storage of food materials. A relatively insoluble substance is 

 formed, hence the concentration can never rise above that 

 of its saturated solution, and as the substance is used more 

 dissolves to keep the solution saturated. 



The further transformations of the carbohydrate will be 

 considered in the next chapter. 



GENERAL REFERENCES 



F. F. BLACKMAN : Phil. Trans., 1895, B, 186, p. 503. 



H. T. BROWN and F. ESCOMBK : Proc. Soc. Roy., 1905, B, vol. 76, p. 29. 



C. TIMIRIAZEFF, Proc. Roy. Soc., 1903, vol. 72, p. 424. 



R. WILLSTATTER and A. STOLL : Untersuchungen tiber Chlorophyll. Berlin, 



