protozoan: Cellular Structure and Function

The various forms have in common a unicellular structure consisting of a mass of cytoplasm with one or more nuclei (see cell). Like all cells, they are bounded by a thin cell membrane; in addition, most have a tough outer membrane called a pellicle, which maintains their form. Despite their small size and lack of organization into multicellular systems, protozoans carry on all the metabolic functions of animals. Organelles, or intracellular structures, carry out a variety of functions, such as digestion, excretion, respiration, and coordination of movement; some protozoans are much more complex in their internal structure than are the cells of multicellular animals.

Sections in this article:

• Introduction
• Reproduction
• Respiration
• Digestion
• Cellular Structure and Function
• Bibliography

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