CHAPTER XV 

 FOOD MANUFACTURE 



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III. SYNTHESIS OF STARCHES 



Some of the sugar in plants may be changed chemicallv to insokible 

 starches and other carbohydrates, to fats and oils, and to proteins. 

 In the body of animals sugar is changed to a starch-like compound 

 called glycogen, and also to fats and oils. While studying such trans- 

 formations we may also appropriately consider many facts about the 

 accumulation and digestion of these foods. In this chapter we shall be 

 interested mainly in the formation and digestion of starch and a few 

 other carbohydrates. 



Starches, fats, and oils are made from sugar alone. Proteins are made 

 from sugar and certain salts of nitrogen, sulfur, and, in some cases, phos- 

 phorus also. These transformations of sugar to other kinds of food are 

 either condensation processes or a combination of oxidation-reduction 

 and condensation processes. The simplest transforaiations, such as the 

 formation of starch from glucose or of inulin from fructose, involve only 

 chemical condensation. We shall first consider the synthesis of starch 

 from sugar. 



Synthesis of starch from sugar. Starch is formed in plant cells from 

 glucose by chemical condensation: 



Glucose > Water + Starch 



n CUnO, > (n - 1)H20 + (C6Hio05)„H20 



The group of enzymes known as diastase apparently catalyzes the 

 process of starch synthesis. Some of the plants in which starch is not 

 formed have been reported to lack one of these several enzymes. Diastase 

 does catalyze the hydrolysis of starch back to sugar in plant cells. This 

 hydrolysis of starch is easily obtained in test tubes with diastase that has 

 been extracted from plants. But the synthesis of starch from sugar 

 is influenced by some condition present in the "starch-forming" plastids 



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