Fungi

Question 1

What are the main characteristics of fungi?

Answer 1

They are heterotrophs therefore need to obtain carbon from another organic source

Question 2

What is the study of fungi called?

Answer 2

Mycology

Question 3

Describe the structure of a fungal cell?

Answer 3

All the same organelles as a plant and animal cell with the addition of a bud, septum and bud scar

Question 4

What are the 2 types of antifungals used to fight fungi?

Answer 4

Polyene Antibiotics
Azole antifungals

Question 5

What do azole antifungals target?

Answer 5

The fungal cell membrane

Question 6

How do the azoles work?

Answer 6

They work on 2 fronts:
By interrupting the lipid bilayer
By poisoning the cell through the build-up of toxic sterols

Question 7

What effect to do azoles have on C.albicans?

Answer 7

They cause the cells to crenellate and shrink in on themselves, due to disruption of the lipid bilayer
They are no longer functional

Question 8

What do the Polyene class do?

Answer 8

They create a ‘death ring’

Question 9

How does the Polyene Amphotericin B work?

Answer 9

Enlarges itself within the membrane
Binds to ergesterol in multiple locations
It then creates channels once enough of them have bound to the ergosterol
Suggesting 8 molecules bound (‘8 member death ring’) forms an ion channel

Question 10

If an ion channel is produced by a Polyene class antifungal, what happens?

Answer 10

Ions leak out of the cell through the ion channel
This changes the osmotic potential
So water moves out of the cell because the water potential is lower outside the cell
Leaving a crenelated cell

Question 11

What are dimorphic fungi?

Answer 11

Fungi that can grow to be either filamentous or yeast depending on what conditions you grow them in

Question 12

What are the 2 structural phases of dimorphic fungi?

Answer 12

Yeast- unicellular
Filamentous- hyphae

Question 13

List the properties of Candida albicans

Answer 13

Dimorphic
Opportunistic pathogen- only strikes as pathogen when the conditions are correct
Commences in the yeast phase- Manageble by hygiene and immune system
Only becomes invasive when in the filamentous phase

Question 14

How can spores reproduce?

Answer 14

Either sexually or asexually

Question 15

Describe the structure of a spore

Answer 15

They have a nucleus, dehydrated cytoplasm, glycogen that forms a coat and a thick spore wall

Question 16

What are the 2 main types of asexual reproduction of spores?

Answer 16

Conidium- individual spores
Sporangiospores- multiple spores in a sac

Question 17

Where are conidia found?

Answer 17

Found on the end of a hyphae (conidiophore)

Question 18

How do penicillium conidia reproduce?

Answer 18

Break off the conidiophores and disperse into the air

Question 19

How do aspergillus conidia structured?

Answer 19

Aspergillus have a vesicle that terminates the hyphae
Protrusions from that are the conidiophores
At end of conidiophores are conidia

Question 20

How do sporangium reproduce?

Answer 20

Sporangiospores in the sporangium
Sporangium sit on a sporangiophore
When spoangiospores are released sporangium wall splits

Question 21

Give the 2 types of fungi hat can reproduce

Answer 21

Imperfect fungi- asexual spores
Perfect fungi- capable of asexual AND sexual reproduction (sexual spores)

Question 22

What are the 3 main types of sexual spores?

Answer 22

Zygomytes
Ascomycetes
Basidomycetes

Question 23

How do zygomycetes reproduce?

Answer 23

Fusion of hyphae from two individual zygospores
Zygospore develops develops a thick cell wall which can be dispersed in the air and spread
For example, bread mould

Question 24

How do Ascomycetes reproduce?

Answer 24

Sexual spores in sac-like ascus that contain 8 ascospores
Produced through 2 rounds of meiosis and 1 round of mitosis
These ascus burst open which release the ascospores into the air
For example, dead mans fingers grown out of wood

Question 25

How do basidomycetes reproduce?

Answer 25

They for a specialised cell called a basidium
There are 4 basidiospores per basidium
Found in the gills of mushrooms
The basidiospores are released into the air on maturaiton

Question 26

List the products of fungi

Answer 26

Toxins- Released a defence mechanism
Antibiotics
Penicillin
Cephalosporin
Mushrooms- Agaricus
Quorn- Fusarium
Citric acid- From Aspergillus

Question 27

List the different type of toxins released by fungi

Answer 27

Mycotoxins; Ergot- produces Alkaloid toxin related to lysergic acid dimetylamide can cause paralysis
Aflatoxins; stored in foods and cause liver damage
Amaminta phalloides- ‘death cap fungus’, causes death
Psilocybin- found in magic mushroomed, psychedelic drugs