PHYSIOLOGY OF MICROORGANISMS 61 



2 C.H 10 3 + ILO^ 

 Starch -f Water = .Maltose 



c'uHaQu + H 2 o = c 6 H, A + C.HUQ. 



Maltose -f- Water r= Dextrose -j- Dextrose 



C 6 H 12 O =_> (J !,()! I -f2 CO, 

 Dextrose =: Kthvl Alcohol -j- Carbon-dioxide 

 r.l 1,011 + 0,=C 8 H 4 2 + H a O 

 Ethyl alcohol -|- Oxygen = Acetic acid -f Water 



r,II 4 O 5 +2 2 = 2 CO 2 -f2 H 2 O 

 Acetic acid -(- Oxygen Carbon-dioxide -(- Water 



It must not be thought that these equations present the 

 entire process. They simply present the chief reactions. 

 For example, the following equation, C H 12 = 2 C 2 H 5 OH 

 + 2 CO,, implies that all of the sugar appears as alcohol 

 and carbon-dioxide. The true reaction is more like the fol- 

 lowing: Dextrose -{- Yeast = Alcohol + Carbon-dioxide 

 -f products of unknown nature + yeast n . In other 

 words, a part of the sugar is used in the formation of 

 numerous products other than the chief by-products, and 

 another part of the sugar is used in building the new yeast 

 cells, for decomposition goes on only as the organisms 

 proliferate. 



Relation of the organism to its by-products. It is evi- 

 dent that, if an organism changes sugar to carbon-dioxide 

 and water, it will derive more energy from a given amount 

 of sugar than will another organism that forms an organic 

 acid from the sugar. The organic acid contains much 

 energy, while the carbon-dioxide and water do not. If the 

 two organisms are to secure an equal amount of energy 

 from sugar, the second must decompose a much greater 

 amount of sugar than the first. With the organism that 

 causes complete decomposition of the sugar the amount of 

 by-products may not greatly exceed that of the mass of 

 cells resulting from the decomposition. In other words, a 

 large part of the food is used for the building of cells. This 

 is made possible by the fact that the organism uses all the 



