What is the structure of the protozoan cell? Why is it an independent organism?

The cell of protozoa is similar in structure to the cells of multicellular, however, it itself represents a whole organism with the processes of nutrition, excretion, reproduction and others characteristic of the organism. For example, the cell of the common amoeba captures food with the help of pseudopods (pseudopodia), the digestion process takes place in the cell, untreated substances are released through the hole in the cell of the powder. Amoeba is capable of reproduction by division. Protozoa have some forms of reflexes and movements with the help of flagella and cilia.