Cellular Structure of Protozoa

Characteristics of Protozoa

• Protozoa are unicellular, eukaryotic, and heterotrophic organisms.
• They can be either free-living or parasites.
• There are approximately 65,000 species of protozoans, categorized into different groups.
• They lack a cell wall.

Cellular Structure

• Protozoa have a eukaryotic cell with a single membrane-bound nucleus.
• The nucleus has a diffused appearance due to scattered chromatin, and contains a central body called endosome or nucleoli.
• Nucleoli of apicomplexans have DNA, whereas those of amoeboid protozoa lack DNA.
• Ciliates have both micronucleus and macronucleus.
• The plasma membrane encloses the cytoplasm and locomotory projections like flagella, pseudopodia, and cilia.

Cell Organelles and Structures

• Some protozoa have a membranous envelope called pellicle, which gives a definite shape to the cell.
• Epibiotic bacteria can attach to the pellicle by their fimbriae in some protozoans.
• The cytoplasm is differentiated into outer ectoplasm and inner endoplasm, with ectoplasm being transparent and endoplasm containing cell organelles.
• Some protozoa have a cytostome for ingesting food, and food vacuoles where ingested food is stored.
• Ciliates have a gullet, a body cavity that opens outside.
• A central vacuole is present in some protozoa for osmoregulation, removing excess water.
• Membrane-bound cell organelles, such as mitochondria, Golgi bodies, lysosomes, and other specialized structures, are present.

Pathogenic Protozoa

• Some protozoa cause diseases in animals and humans, such as Plasmodium (malaria), Trypanosoma (sleeping sickness), and Trichomonas (trichomoniasis).

This quiz covers the cellular structure of protozoa, including their unicellular eukaryotic nature, specialized internal structures, and unique characteristics of their nucleus and membranes.