LIFE FUNCTIONS OF AN AMOEBA 



43 



VII. Name a function performed by the amoeba that the green cell cannot 

 perform. What is the value of this function to an animal organism ? 



VIII . Make a drawing three inches in diameter, of an amoeba, and label 

 cytoplasm, nucleus, plasma membrane, pseudopodia, and vacuole. 



Life functions of an amoeba. Ingestion. When an amoeba 

 comes in contact with a particle of food, it throws out pseudopo- 

 dia which flow over and around the food. The food particle is then 

 taken into the cytoplasm. This engulfing of food by the amoeba 

 is its method of food getting, or ingestion. The amoeba shows little 

 power of selection of food. It takes in almost anything small enough 

 to be engulfed. The cytoplasm encloses the food and forms a vac- 

 uole or bubble encircled by plasma membrane. The food and 

 some fluid deposited by the cytoplasm are inside the vacuole. 



Digestion. The engulfed food is principally smaller microor- 

 ganisms and particles of plants. These consist of combinations of 

 the nutrients, proteins, fats, and carbohydrates. The particles cir- 

 culate in the streaming cytoplasm in the form of a food vacuole. 

 The cytoplasm secretes 



digestive enzymes to con- /;" |^ g,!:^^4xjoLvttcuoie 

 vert these nutrients into a 

 soluble form which can 

 then be assimilated by the 

 protoplasm. As the circu- 

 lating protoplasm carries 

 the food around the cell, 

 the digestive enzymes, pro- 

 tease, lipase, and amylase, 

 gradually dissolve the nu- 

 trients in the food. These 

 nutrients pass through the 

 plasma membrane of the vacuole by osmosis and mingle with 

 the cytoplasm. The indigestible materials that have entered with 

 the food may be eliminated from any part of the organism. 



■la^toplctsm /;/--- ps«uaopo2L 





nxccleus 



contrctctlle 

 Vrccouole 



Amoeba may assume a variety of shapes. Compare 

 the animals you studied imder the microscope with 

 these diagrams. 



