3.0 Fungi Flashcards Preview

MedST IB: Biology of Disease (BoD) > 3.0 Fungi > Flashcards

Flashcards in 3.0 Fungi Deck (25)
Loading flashcards...
1

Fungal cell wall is mainly composed of _______________
Glucan = polymer of ___________
Mannan = polymer of __________

Fungal cell wall is mainly composed of polysaccharides
Glucan = polymer of glucose
Mannan = polymer of mannose

2

Plasma membranes of fungi contain ________

Plasma membranes of fungi contain ergosterols

3

What is the structure of the fungal cell wall?

1) Inner chittin layer
Long straight chain
β-1,4-linked N-acetylglucosamine

2) Outer glucan layer
Branched chain
β-1,3-linked glucose

3) Embedded glycopeptides
Asparagine - N-linked mannose/galactose
Serine/threonine - O-linked mannose/galactose

4

What is the structure of yeasts?

Unicellular
Round/oval
(candida can have pseudohyphae structure)

5

What two types of mitosis occurs in yeasts?

1) Symmetrical binary fission
2) Asymmetrical budding

6

What is the structure of filamentous moulds?

Multicellular
Hyphae (thin, branching cylinders)
Can be septate or aseptate
Mycelium = interwoven mass of hyphae

7

How does mitosis occur in hyphae?

Apical growth
-Mitosis only occurs at tips/side branches

8

What are dimorphic fungi?

22 degrees = filamentous morphology

37 degrees = Yeast

9

Brief overview of asexual reproduction:

Occurs most of the time

Spores produced by mitosis
Yeasts → internal spores
Moulds → external spores (condida) or internal spores (sporangium)

10

What fungal species only reproduces using asexual reproduction?

Deutermycota

11

Brief overview of sexual reproduction:

Haploid fungus → sexual structures (motile gametes or sexual hyphae)

2 x sexual structures fuse → nuclei fuse → diploid → re-assortment and recombination

12

What are the three different types of sexual spores?

1) Ones that form internally within tubules (Ascus)
2) Ones that form externally on club like structures (Basidium
3) Ones that form from fusion of sexual hyphae

13

Complete the following statements regarding the nutrition of fungi:

• Fungi rely on preformed ______ compounds as sources of energy and carbon
• Secrete enzymes into the environment ⟶ ___________
• Absorb simple soluble molecules through ___________
• Yeasts live in _______ environments
• Hyphae __________ food material

• Fungi rely on preformed organic compounds as sources of energy and carbon
• Secrete enzymes into the environment ⟶ extracellular digestion of food material
• Absorb simple soluble molecules through channels in the fungal cell wall
• Yeasts live in moist environments
• Hyphae penetrate into food material

14

Define saphrotrophs:

Fungi that feed on dead plant or animal material

Majority of fungi

15

What metabolites can fungi produce?

1) CO₂
2) Ethanol
3) Antibiotics - Pencillin, cephalosporin, streptomycin
4) Immuno-suppressants - ciclosporin
5) Other drugs - ergometrine, ergotamine
6) Toxins - alphatoxins

16

What are lectins?

Proteins that have a specific carbohydrate recognition domain (many fungal PRRs are lectins)

17

List 6 fungal PAMPs and their PRRs:

1) Mannose-rich structures
- Mannose binding lectin (MBL) ← soluble
- DC-sign
- Mincle

2) β-1,3-glucan
- Dectin-1

3) Mannans
- Dectin-2

4) Phosphidolipidomannans
- TLR2

5) O-linked mannose
- TLR4

6) N-linked mannose
- Mannose receptor

18

What defects in host defences can lead to increased fungal infections?

1) Impaired fungal sensing (β-1,3-glucan)
- ↑ superficial infections
- Dextrin-1 deficiency
- CARD9 mutation

2) Impaired IL-17 immunity
- ↑ superficial infections
- IL-17 receptor deficiency
- Autoantibodies (anti IL-17/22)

3) Impaired neutrophils
- ↑ deep infections (Aspergillus)
- Post-chemo
- Inherited

4) Impaired T-cells/macrophages
- ↑ superficial + deep infections (Yeast + dimorphic)
- AIDs/transplant

19

What occurs following ingestion of the fungal toxin ergotamine?

It is a potent vasoconstrictor → ischamia and gangrene of digits

20

What is a common commensal fungus?

Candida albicans (throat, gut and vagina)

21

What is another name for superficial fungal infections?

Ringworm

22

Examples of superficial fungal infections:

1) Dermatophye moulds
- Common
- Spores transmitted by person-to-person contact / sharing clothing
- Chronic infection → toxins → Type IV hypersensitivity

2) Candida Albicans
- Chronic finger nail infection

3) Malassezia furfur
- causes pityriasis versicolor (blotchy skin rash - does not tan)

23

Example of subcut fungal infection:

Rose picker's disease (dimorphic sporothricx schenckii)

24

Examples of systemic pathogens:

Histoplasma capsulatum

25

Examples of systemic opportunists:

Candida
Pneumocystis jirovecii
Cryptococcus neoformans
Aspergillus fumigatus
Mucor