GENERAL BIOLOGY 



In addition to the foregoing forms of energy 

 protoplasm utilizes its latent energy to produce 

 the characteristic products that have already been 



described. These 

 include, besides 

 the food reserves, 

 such as fat, starch 

 granules, egg- 

 yolk, etc., minute 

 quantities of 

 other substances 

 (zymogens and 

 hormones) which 

 enable the cell 

 to accomplish its 

 multitudinous re- 

 actions with the 

 minimum ex- 

 penditure of en- 

 ergy. 



Enzymes and 

 Enzymotic Reac- 

 tions. If starch 

 be taken into the 

 mouth or placed 

 in a test tube with 

 saliva, it is acted upon by the saliva and its mole- 

 cules are split into their sugar elements, in which 

 form they may be absorbed through the lining wall 

 of the digestive tube. The chemist can also boil 



FIG. 31. The firefly; the one on the 

 ground shows the phosphorescent organs (the 

 three white segments of the abdomen). 

 (From Linville and Kelly.) 



