Protozoa - Amoebae

Question 1

Name the basic groups of traditional parasites.

Answer 1

1. helminths 2. protozoa

Question 2

How do Helminths & Protozoa differ?

Answer 2

helminths - multicellular, platyhelminths, nematoda vs. protozoa - unicellular

Question 3

What are some characteristics of the protozoa?

Answer 3

1. diversity 2. unicellular eukaryotes w/ membrane bound nucleus (chrs) & organelles 3. heterotrophs: ~45,000 spp identified in all environment, very significant in their health impact on humans

Question 4

What is one characteristic common to all the members of the Phylum Sarcomastigophora?

Answer 4

1. subphylum sarcodina is characterized by having pseudopodia 2.subphylum mastigophora is characterized by presence of flagella

Question 5

What is one characteristic common to all the members of the Phylum Ciliophora?

Answer 5

presence of cilia

Question 6

What is one characteristic common to all the members of the Phylum Apicomplexa?

Answer 6

presence of apical complex

Question 7

What are the 4 genera in the order Amoebida?

Answer 7

1. Entamoeba
2. Endolimax
3. Idoamoeba
4. Acanthamoeba

Question 8

Naegleria is classified in which order?

Answer 8

Schizopyrenida

Question 9

Name the three orders in which members posses a flagellum.

Answer 9

1. Diplomonadida (Giardia lamblia)
2. Trichomonadida (Trichomonas vaginalis)
3. Kinetoplastida (Trypanosoma + Leishmania)

Question 10

Which genera are found in the phylum Apicomplexa?

Answer 10

Plasmodium + toxoplasma

Question 11

Describe flagella

Answer 11

mastigophora
trophozoite stage - one or more flagella extending from it
swim - can be in a liquid medium
cytoplasmic extension surrounded by plasma membrane
axoneme - embedded in flagellum provides support
basal body (aka blepharoplast, kinetosome) anchors flagellum

Question 12

Describe pseudopodia

Answer 12

amoebae
used for locomotion & food acquisition
temporary extensions of cytoplasm & plasma membrane
depend on actin & myosin
requires substrate

Question 13

Describe cilia

Answer 13

smaller & more numerous than flagella

Question 14

Do all protozoa have mitochondria?

Answer 14

no
present in some species:
cristae - tubular shape
muticellular eukaryotes have 1 amellar (flat) cristae
absent in some species:
anaerobia metabolism

Question 15

Where do organisms in the order Amoebida live?

Answer 15

most are free living

some in vertebrate or invertebrate intestinal tracts

Question 16

How do Amoebida reproduce?

Answer 16

binary fission - asexual

Question 17

What types of symbiotic relationships with humans are possible?

Answer 17

most are commenals (+/0): amoeba benefits, no effect on humans
few are pathogenic

Question 18

Which genera of Amoebida are associated with humans?

Answer 18

1. entamoeba
2. endolimax
3. lodamoeba

Question 19

How are the 3 genera of Amoebida assoicated with humans differentiated?

Answer 19

differ in size & nucleus structure - major features used to identify species

Question 20

In the nucleus of organisms in the genus Entamoeba, how can the chromatin be distributed?

Answer 20

varies among species

Question 21

What is an endosome and how is it useful in identification?

Answer 21

in nucleus
similar to nucleolus - contains RNA & genes for ribosome synthesis
size & position of endosome in the nucleus are important features in making identification
size: small vs. large
location: centric (middle) vs. eccentric (off to side)

Question 22

What two stages occur in the life cycle of Entamoeba?

Answer 22

1. trophozoic - feeding stage
stage found inside the host
2. cyst
survives external environment
infective stage/transmission stage

Question 23

What are chromatoidal bars and in which stage of Entamoeba are they found?

Answer 23

deposits of nucleic acids
morphology varies
in most species - only found in young cysts
in old cysts - disappears & disintegrates
presence or absence - gives age

Question 24

How many people worldwide are affected by Entamoeba histolytica?

Answer 24

~500 million infected

~110,000 deaths / year

Question 25

What is the size of a trophozoite?

Answer 25

~25mm in diameter

Question 26

Describe the morphology of the nucleus of Entamoeba histolytica.

Answer 26

endosome - small & centric | PC - fine, evenly distributed

Question 27

How do the trophozoites reproduce?

Answer 27

binary fission daughter cells move away from each other ~1/3 of dividing cells can't break apart

Question 28

What happens if the two daughter cells can’t break apart?

Answer 28

release chemoattractant - attracts a midwife cell | midwife cell ruptures cleavage furrow

Question 29

What stimulates encystment?

Answer 29

drying out to encyst

Question 30

What is a precyst?

Answer 30

lots of glycogen - energy | secretes - cyst wall

Question 31

How many times does the nucleus undergo division in the cyst

Answer 31

2 divisions. | 1-2-4

Question 32

What does the chromatoidal bar look like?

Answer 32

long with rounded ends

Question 33

What is a mechanical vector and how is it relevant in this life cycle of Entamoeba histolytica?

Answer 33

fecal oral route uses mechanical vector vector actively moves parasite but no parasite development ex: flies & cockroaches

Question 34

What happens when the cyst is ingested by a human?

Answer 34

resistant to gastric acids encysts in SI - trypsin helps break down cyst wall cytoplasm & nuclei divide - 8 metacystic trophozoites move to LI

Question 35

Noninvasive intestinal disease is caused by which stage of Entamoeba histolytica?

Answer 35

cyst stage

Question 36

Why are asymptomatic individuals the main source of infection in Entamoeba histolytica?

Answer 36

carrier are the same source of infection - ovivirulent

Question 37

What is a secretagogue?

Answer 37

substance that stimulates secretion of another substance stimulates increased mucus secretion by host body secretes so much it runs out of mucus

Question 38

What is stimulated by the E. histolytica secretagogue?

Answer 38

mucus secretion

Question 39

What is a lectin?

Answer 39

protein which has a high binding specificity for a particular CH2O

Question 40

How is the Gal/GalNAc lectin of E. histolytica involved in invasion?

Answer 40

trophs binds surface of host cell (cytoadherence)

Question 41

What is an amebapore?

Answer 41

small peptides that come together to form hexamers | hallow structure

Question 42

How does amebapore peptide affect the host cell membrane?

Answer 42

inserts itself into host plasma membrane, bores a hole host cytoplasm leaks out host cell dies

Question 43

How do E. histolytica cysteine proteases affect the host?

Answer 43

cleave the host cells & cause tissue damage

Question 44

What happens if the E. histolytica trophozoites advance into the submucosa?

Answer 44

ulcer deepens & spreads laterally | forms flask-shaped ulcer

Question 45

What are the symptoms of E. histolytica infections?

Answer 45

diarrhea, dysentery, cramps, flatulence, nausea circulation becomes inadequate: sheets of epithelial cells slough off, bleeding, loss of electrotytes 10-20 stools/day fever deydration - big problem in children

Question 46

What is acute necrotizing colitis?

Answer 46

severe form of E. histolytica infection blood diarrhea, fever, pain most of mucus depleted mortality exceeds 50%

Question 47

What is an ameboma?

Answer 47

inflammatory thickening of intestinal wall around ulcer painful can by confused with tumors

Question 48

How can perianal ulcers form in an E. histolytica infection?

Answer 48

trophs invade skin around anus

Question 49

How are infections with E. histolytica diagnosed and treated?

Answer 49

``` diagnosis: fecal -cysts only useful for luminal amebiasis (non-invasive) ELISA - antibodies treatment: metronidazole - inhibit NA synthesis surgery antibodies ```

Question 50

How can this parasite be controlled?

Answer 50

sanitation: removing pathogens from drinking water sand filtration - water goes through sand, large particles like cysts are trapped in the sand