Fungi

Question 1

Definition of Fungi.

Answer 1

Fungi are eukaryotic organisms which lack chlorophyll and vascular tissues and can range in form from single cells to a body mass of branched filamentous hyphae that can often produce fruiting bodies.

Question 2

How are fungi different from other eukaryotes?

Answer 2

1. Contain a rigid cell wall made of chitin, glucans and glycoproteins.
2. Contain plasma membrane made of ergosterol instead of cholesterol.

Question 3

Name the 4 phyla of fungi.

Answer 3

1. Zygomycota
2. Basidiomycota
3. Ascomycota
4. Deuteromycetes

Question 4

What is the word for infection caused by fungi?

Answer 4

Mycosis/Mycoses.

Question 5

What are the 3 ways fungi can cause disease in humans?

Answer 5

Allergy
Infection
Mycotoxins

Question 6

What are the 2 morphological forms of fungi?

Answer 6

Yeast - unicellular

Moulds - multicellular and filamentous

Question 7

Define dimorphism.

Answer 7

The ability to switch morphology.

Question 8

How do yeasts and moulds reproduce?

Answer 8

Yeast - reproduction by budding - asexual

Moulds - reproduce by asexual or sexual spores

Question 9

What does fungal cell membrane consist of?

Answer 9

Glycoproteins
Phospholipids
Ergosterol

Question 10

Why is having an ergosterol cell membrane important?

Answer 10

Maintains structure and function of fungal cell.
Allows for selective toxicity - Ergosterol biosynthesis pathway is a common target of antifungal treatment. Can damage fungal cells but not human cells.

Question 11

Outline an application of chitin in medicines/pharmaceutical industry.

Answer 11

Chitin is a non-toxic and biocompatible thus can be used in medical devices.

Question 12

What two techniques can a diagnostic lab use to identify fungal species?

Answer 12

1. Microscopic observations with staining processes

2. Inoculation of agar, allowing selective growth of specific fungi.

Question 13

Specialised labs can used ELISA tests and PCR to identify fungal species? What does an ELISA test and PCR do?

Answer 13

ELISA - Can detect antibodies of specific antigens.

PCR - Can detect specific nucleic acids of fungal species.

Question 14

What are the 2 morphological stages, multicellular fungi display?

Answer 14

Vegetative

Reproductive

Question 15

What class do yeasts belong in?

Answer 15

Ascomycetes

Question 16

Describe the process of budding in yeasts (4).

Answer 16

Budding is an asexual method of reproduction in many yeasts.

1. Formation of small outgrowth/bud from the parent cell.
2. As bud forms the nucleus of the parent divides and one daughter nucleus enters the bud.
3. The bud increases in size and chitin is laid down where the bud will extrude.
4. The bud eventually breaks away from the parent.

Question 17

How are hyphae divided?

Answer 17

Hyphae are divided into separate cells by cross-walls called septa/septum.

Question 18

What is mycelium?

Answer 18

These are intertwining mass of hyphae.

Question 19

What 2 types of mycelium are there and what are their characteristics?

Answer 19

Vegetative and Aerial/reproductive
Vegetative - penetrate into the growth media and absorbs nutrient or grows on surface.
Aerial - projects above the surface.

Question 20

Outline 5 steps for formation of sporangiospore.

Answer 20

1. Tip of hypha enlarges.
2. Septum divides from the rest of the hypha.
3. Nuclear division occurs repeatedly and each nucleus becomes encased by an outer cell.
4. When the sporangium is ruptured, the spores are scattered widely.
5. The sporangiospores can germinate if conditions are suitable to form a new mycelium.

Question 21

What is superficial mycoses?

Answer 21

Caused by fungi which invade the superficial
keratinized tissues (i.e. skin, hair and nails) but not
the deeper tissues.
They can use keratin as nutrient source.

Question 22

Name 6 antifungal drugs.

Answer 22

Polyenes
Azoles
Allylamines
Echinocandins
Griseofulvin 
Nucleosides