Protozoa Structure and Nutrition

Study Notes

Pellicle provides rigidity and maintains a distinctive shape in some protozoa.
Cytoplasm is divided into ectoplasm (outer, transparent) and endoplasm (inner, organelle-containing).
Pseudopodia are used for movement and food capture, especially noted in amoebas.
Some protozoa have a cytosome for fluid and particle ingestion.
Contractile vacuoles in organisms like Naegleria regulate water balance.
Apicomplexa lack external locomotion organelles but employ subpellicular microtubules for movement.
Distinct structures include Golgi apparatus, mitochondria, lysosomes, and food vacuoles.

All protozoa are holozoic, requiring organic matter either in solution or particulate form.
Amebas use temporary mouths to engulf food, digest within food vacuoles, and eject waste.
Permanent mouths, cytosomes or micropores, allow for continuous food intake.
Pinocytosis involves drawing in fluid nutrient material via openings in the cell wall.

Protozoa reproduce asexually and sexually; binary fission is the most common asexual method.
Cysts released in feces can survive external environments for days up to a year.
Oocysts, formed via sexual reproduction, are significant in the Apicomplexa group.

Direct transmission: Infections spread through intimate body contact (e.g., Trichomonas spp.).
Faecal-oral transmission: Involves environmentally resistant cysts ingested from contaminated food or water (e.g., Entamoeba histolytica).
Vector-borne transmission: Blood-sucking arthropods transfer trophozoites to new hosts (e.g., Trypanosoma brucei).
Predator-prey transmission: Cysts in prey tissues are ingested by predators, allowing the cycle to continue (e.g., Toxoplasma gondii).

Kingdom: Protozoa consists of various phyla such as Sarcodina, Mastigophora, and Apicomplexa.
Sarcodina encompasses amoeboid forms that may be free-living or parasitic, characterized by pseudopodia.
Asexual reproduction typically occurs through binary fission, multiple fission, or sporulation.

Order Amoebida includes various entozoic amebas found in human or animal intestines, such as Endamoeba and Entamoeba.
Entamoeba histolytica is notable for causing serious conditions like amebic dysentery.

Typical life cycles involve infection through cyst ingestion, trophozoite activity in the intestine, and potential spread to other organs.
Toxoplasma gondii has a complex life cycle involving both intestinal and extraintestinal stages across different animal hosts.

Plasmodium causes malaria, a severe disease affecting humans, with significant mortality in sub-Saharan Africa.
The species responsible for malaria include P. falciparum, P. vivax, P. ovale, and P. malariae.