8 Fungi and Parasites (Midterm 1 up to here) Flashcards
These organisms can be either unicellular or multicellular.
Fungi
Internal, membrane-bound structures of fungi are similar to those of eukaryotes, but differences b/w fungi and euk. are found in the cell envelope of fungi. What are these two differences?
- Ergosterol > sterol cmpnd found in fungal plasma membrane
2. Chitin > rigid, multi-layered carb structure (like bacterial PG) lying above plasma membrane
Fungi exist as two diff morphological types:
- ____
- ____
- Yeasts
2. Molds
Are yeasts single-celled or multi-cellular?
yeasts = single-celled fungi
Are molds single-celled or multi-cellular?
molds = multicellular fungi
This type of fungus reproduces by budding.
yeast
This type of fungus reproduces via a “spore” stage.
mold
This type of fungus forms filamentous structures called “hyphae”, a collection of which is called a “mycelium”.
mold
What are dimorphic fungi able to do?
Alternate b/w yeast and mold forms, depending on the envir
T or F: Relatively few fungi cause disease, but the diseases are usually severe.
T
List the three types of fungal diseases.
- Hypersensitivity diseases
- Mycotoxicoses
- Mycoses
Fungal hypersensitivity diseases are allergic responses to fungal ____ and ____.
spores, metabolites
What is a mycotoxicosis?
A poisoning due to ingesting a fungal metabolic product.
What is a mycosis?
An infection due to growth of fungus in/on a human host.
How are mycoses classified?
According to how DEEPLY the fungus penetrates tissues.
3 types of mycoses?
- Cutaneous (superficial)
- Subcutaneous
- Systemic (deep)
Cutaneous mycoses are caused by ______, fungi who use keratin as a nutrient source
dermatophytes
These types of mycoses are often associated w/ cuts or wounds.
Subcutaneous mycoses
These are fungal infections of internal organs.
systemic (deep) mycoses
These types of mycoses are associated w/ fungal growth on the outermost layers of the skin, nails, etc.
cutaneous (superficial) mycoses
These types of mycoses are characterized by fungal infections of deeper skin and subcutaneous tissues.
Subcutaneous mycoses
These types of mycoses can be VERY SEVERE.
Systemic (deep) mycoses
This type of fungus is found asymptomatically as part of normal human flora
Candida (a yeast)
How are fungal infections diagnosed in the lab? (2)
- Direct microscopic examination
2. Growth on culture media > biochemical identification
Why is it difficult to achieve “selective toxicity” w/ antifungal medications?
Fungi and humans are BOTH eukaryotic, so meds that target fungal cells can also target human cells > potential toxicity
Anti-fungals usually have two modes of action. What’re they?
- Target fungal cell envelope
2. Interfere w/ DNA/RNA synthesis
What’re parasites?
organisms that reside in or on a mammalian host as part of its lifecycle
T or F: Parasites can be either eukaryotic or prokaryotic.
F
Parasites are only eukaryotic
What’re the two taxonomic gps of parasites?
- Protozoa
2. Helminths (metazoa)
These types of parasites are microscopic only
protozoa
These types of parasites can be either microscopic OR macroscopic
helminths
These types of parasites are multicellular worms
helminths
These types of parasites are similar to yeast in size and internal complexity
protozoa
These types of parasites have differentiated organs/tisues
helminths
What’re the two morphological forms that some protozoa can alternate between?
- Trophozoite
2. Cyst
Trophozoite or cyst?
Metabolically active and replicative protozoan form found inside the host.
Trophozoite
Trophozoite or cyst?
Dormant, non-replicating form of protozoan w/ a thickened wall to facilitate survival.
Also, this is the form that’s gets transmitted from host to host.
Cyst
What’re the three types of helminths that’re of human importance?
- Nematodes
- Tapeworms
- Flukes
Are helminths usually microscopic or macroscopic?
Macroscopic
How do helminths reproduce?
Via eggs that hatch into larvae and grow into adult worms
Infective form of helminth?
Eggs/larvae
What’re the two taxonomic gps of parasites?
- Protozoa
2. Helminths (metazoa)
This form of helminth causes symptoms of disease.
Adult worms
How’re giardiasis parasitic infections transmitted?
fecal-oral route
Is giardiasis caused by helminths or protozoa?
Protozoa
How is the cyst form of Giardia lamblia (causes giardiasis) converted into the trophozoite form in vivo?
Stomach digestive enzymes degrade the cyst wall, triggering conversion to trophozoite form in the intestinal tract
T or F: Amoebic meningitis is a common CNS infection caused by Naegleria fowleri (parasitic protozoan)
F
This type of CNS infection is extremely rare.
Amoebic meningitis has a fatality rate of almost 100%.
T
What’s the infective form of N. fowleri?
a) Amoeboid trophozoite
b) Flagellate trophozote
c) Cyst
a)
From where must N. fowleri enter through in order to cause infecton?
Nasal mucosa
Another name for N. fowleri?
“Brain-eating amoeba”
What is one of the most common helminth infections?
Pinworms
How’re parasitic infections usually diagnosed?
Microscopic examination
T or F: There’re few anti-parasitic agents in clinical use
T
