Protozoa 1.2 ✅ Flashcards
Explain the morphology of a protozoan.
- it is a ‘plastic organism’, changes in form are restricted by the ‘pellicle’
- form of protozoans varies considerably:
floating species: universal symmetry
sessile (immobile) types: radial symmetry - some protozoans have siliceous skeletons
Explain the function of the flagella. What is the flagella made out of? How many to protists posses?
WHEN?
- flagella is used for the active stages
WHAT?
- it consists of a sheath enclosing a matrix (axoneme extends from the cytoplasm)
- self-replicating structure (arises in fission)
WHY?
- used in locomotion
- extends forward and to the side when ‘swimming’
MORE?
- certain organelles can be attached to it
NUMBER?
- protozoans have 1 to two flagellas
Explain the function of the cilia. What is the flagella made out of? How many to protists posses?
WHAT?
- shorter than the flagella but similar in structure
- entails complex fibrillar systems
- delicate fibril
WHY?
- helps support the cortex and ciliary system
- offers support and functions in coordination
Explain the function and existence of pseudopodia.
Pseudopodia are lopodia with
- rounded tips,
- ectoplasm more dense than endoplasm.
Pseudopodia are used for locomotion.
How do larger pseudopodia look?
Larger pseudopodia=granular endoplasm and clear ectoplasm.
Explain the function and existence of trichocysts.
Trichocysts are minute structures that release filamentous or fibrillar threads when discharged.
FUNCTION:
1) serve in the secretion of cyst walls and similar materials.
2) anchor a feeding ciliate
3) may induce paralysis of pray
State the multiple inclusions of protozoa.
nuclei
food vacuoles
chromatophores
stigmas
elimination vesicles
mitochondria
golgi material
pinocytotic vacuoles
stored food materials
endoplasmic reticulum
pigments
small vacuoles
ribosomes
(TYPICALLY LACK CELL WALLS AND CHLOROPLASTS)
Describe Entamoeba histolytica.
Where is it found?
What can the cyst contain?
What happens to the cysts when nuclear division takes place?
Entamoeba Histolytica is part of the Sarcodina phylum.
- present in the LUMEN of the colon (LARGE INTESTINE)
- cysts may contain glycogen vacuoles and chromatoid bodies
- nuclear division results in a quadrinucleated cyst, and the chromatoid bodies and glycogen vacuoles dissapear.
Describe Entamoeba histolytica.
What does it look like?
How does it cause disease?
- cytoplasm has two zones: the outer margin and granular region
- may contain red blood cells (if ingested)
- has a nuclear membrane lined by granules of chromatin (with small central bodies)
- Entamoeba histolytica invades the intestinal epithelium and dorms discrete ulcers. Later the trophozoites multiply and accumulate
it looks like a smiley face
Explain what diseases come from the Phylum Mastigophora.
2 distinct types of human trypanosomes:
1) TRYPANOSOMA BRUCEI GAMIBIENSE:
- “African sleeping sickness”.
- transmitted by tsetse flies
2) TRYPANOSOMA CRUZI:
- “Chagas disease”
- American
- transmitted by “kissing bugs” (sand flies)
How does TRYPANOSOMA BRUCEI GAMIBIENSE look like?
- appear in the blood as TRYPOMASTIGOTES
- elongated bodies
- flagellum (bordering the free edge of the membrane, whip-like extentsion)
What is a “kinetoplast”?
circular DNA inside the single mitochondrion
How does TRYPANOSOMA CRUZI look like?
- large rounded terminal kinetoplast
- difficult to distinguish from African Trypanosoma
- tissue forms develop as amastigotes that multiply after the invasion of a host cell or paracite
What are the developmental stages of TRYPANOSOMA CRUZI?
Three main stages:
1) EPIMASTIGOTES in the vector
2) TRYPOMASTIGOTES in the bloodstream
3) AMASTIGOTES in a rounded cellular stage
What does LEISHMANIA look like? How does it infect the host?
- the ‘sand fly’ transmits infective PROMASTIGOTES during a bite
- PROMASTIGOTES rapidly change into AMASTIGOTES (after phagocytosis by macrophages)
- the infected cell BURSTS
- released parasites are again PHAGOCYTOSED.
Explain how an infection works when infected with the phylum Sporozoa.
How many species of Plasmodium cause malaria?
Which are the most common species?
Which are the most pathogenic species?
Which types of mosquitos transmit the disease?
How is the disease transmitted? How does it get into the bloodstream?
What is this cycle called?
- there are 4 main species of plasmodium:
1) plasmodium vivax
2) plasmodium falciparum
3) plasmodium malariae
4) plasmodium ovale
the most common is:
1) plasmodium vivax
2) plasmodium falciparum
the most pathogenic is:
2) plasmodium falciparum
The sporozoa is transmitted to humans by the bloodsucking bite of a FEMALE ANOPHELES mosquito.
- with the bite SPOROZOITES are INJECTED into the bloodstream
- SPOROZOITES enter PARENCHYMAL cells of the LIVER (first stage of development takes place)
- multiple MEROZOITES rupture and leave the liver cells and INVADE ERYTHROCYTES.
(merozoites do not return to the liver from the red blood cells. parasites in red blood cells continue to multiply breaking out of their host cell synchronously)
PARENCHYMAL CELLS
the cycle is called the “erythrocytic cycle”
What happens during the erythrocytic cycle?
- certain MEROZOITES enter red blood cells and become DIFFEREENTIATED as male or female GAMETOCYTES.
- the gametocytes are ingested and taken up by the ANOPHELES mosquitoes.
When does the resurgence of an erythrocytic infection take place? (relapse)
when MEROZOITES form HYPNOZOITES in the liver breakout and ARE NOT PHAGOCYTOSED in the bloodstream.
Explain toxoplasma gondii.
How does the infection occur?
- infects a wide variety of animals and birds
- the final hosts are strictly cats
- organisms invade the mucosal cells of the cat’s small intestine (form schizonts or gametocytes)
- after sexual fusion, oocysts develop, and exit from the cats lumen via the feces.
- the environmentally resistant cysts become infective after 1-5 days.
