Fungi

Question 1

Fungi can be broadly split into ____ groups. The groups are _____. Some fungi are said to be ____ as they can ____.

Answer 1

Fungi are broadly split into two groups. Yeast (unicellular) or mould (multicellular) consisting of hyphae. Some fungi are said to be dimorphic as they can exist as either a yeast or a mould depending on the enviromental factors.

Question 2

The major components of fungal structure are _____ (7 answers)

Answer 2

1. The cell wall 2. Chitin
2. Hyphae 4. Mycellium
3. Septum 6. Coenocytic hyphae
4. Woronin bodies

Question 3

Describe the fungal cell wall

Answer 3

The cell wall of a fungi consists of chitin ( a major polysacharide component) and β-glucans. It also contains hydrophobins that repel water.

Question 4

Explain the term Chitin.

Answer 4

Chitins are major polysacharide component found in the cell wall of most fungi.

Question 5

Describe hyphae generally and mention it’s sub-types.

Answer 5

Hyphae are long thread like filaments which form moulds. They have an outer cell wall and a hollow lumen which contains cytoplasm and organelles as well as a cell membrane surrounding the cytoplasm. The two forms of hyphae are vegetative hyphae and reproductive hyphae.

Question 6

State the functions of 1. Vegetative hyphae and 2. Reproductive hyphae

Answer 6

1. Vegetative hyphae form mycelia and enable the fungus to obtain nutrients from it’s enviroment whilst anchoring it in it’s substrate
2. Reproductive hyphae form reproductive spores.

Question 7

Describe the different septa which appear in septate hyphae.

Answer 7

The hyphae is tubular in shape and divided by walls called a septum. Primary septa occur at regular intervals throughout the hyphae and contain pores in the cross walls to allow cellular contents to pass. Secondary septa appear randomly throughout the hyphae, forming distinct barriers through which cellular contents cannot cross.

Question 8

What are the names given to hyphae which do not form septa?

Answer 8

Aseptate or coenocytic

Question 9

Explain what is meant by Woronin bodies.

Answer 9

Woronin bodies are organelles which contain hexagonal crystals and are typically located next to the septae. They prevent excessive loss of hyphal contents if the hyphae is damaged.

Question 10

Explain the term coenocytic hyphae.

Answer 10

Coenocytic or aseptate hyphae are hyphae which are not compartmentalized by septa.

Question 11

What is meant by mycellium?

Answer 11

Mycellium is a term for a mass of hyphae

Question 12

What is the optimal temperature range for mesophillic fungi?

Answer 12

15C to 30C

Question 13

What is meant by Saprotrophs

Answer 13

Saprotrophs describe an organism (in this case a fungus) which obtains it’s nutrients from decaying organic matter.

Question 14

Explain the process by which saprotrophs obtain nutrients.

Answer 14

Saprotrophs obtain nutrients through exodigestion. They use enzymes secreted and used outside the organism known as exoenzymes, which breaks down large organic molecules outside of the cell (eg cellulose into glucose) which can then be absorbed by the hyphae as nutrients in a process known as absorpitive nutrition. The nutrients can then pass throughout the mycellium through cytoplasmic streaming.

Question 15

Explain the following terms

1. Xerotolerant fungi
2. Fungistatic
3. Fungicidal

Answer 15

1. Fungus which can grow in low water enviroments
2. An agent which can prevent the growth of fungi without necessarily killing the fungi
3. An agent which kills fungi and prevetns the growth of further fungi.

Question 16

Describe the characteristics of a zygomycota

Answer 16

The main identifying characteristic of a zygomycota is the formation of a zygospore during sexual reproduction. Zygomycota don’t contain hyphal cell walls (they are aseptate / coenocytic) except in its reporductive structures.

Question 17

Describe asexual reproduction in zygomycetes.

Answer 17

Sporangiospores are produced via mitosis in specific hypha known as sporangium. The spores are formed in the sporangium after mitosis has split the cytoplasm of into seperate parts through mitosis. Each part is surrounded by a wall, forming a sporangiospore.

Question 18

Describe sexual reproduction in zygomycetes.

Answer 18

The hypahe of two opposing mate type zygomycetes fuse (plasmogamy) and form a diploid nucleus (after karyogamy), creating a diplod sexual spore. The zygospores form inside a zygosporangium. The zygospores are produced when conditions are unfavourable. Upon germination the zygospore undergoes meiosis to produce haploid hyphae.

Question 19

Describe asexual reproduction in ascomycotes.

Answer 19

Haploid spores called conidia form via mitosis on the end of an aerial hyphae called a conidiophore

Question 20

Describe sexual reproduction in ascomytcetes.

Answer 20

The sexual spore is formed by the fusion of haploid hyphae of opposite mating types to form a diploid nucleus within a sac called an ascus. The ascus in turn is contained with special fruiting bodies known as ascocarp. The diploid nucleus then undergoes meiosis and one round of mitosis to form 8 haploid spores called ascospores.

Question 21

Name and describe a beneficial fungi

Answer 21

Penicillium chrysogenum produces penicillin as a secondary metabolite. The penicillin can then be purified and administered as an anti-bioteic to fight bacteial infection.

Question 22

Name and describe an indirectly beneficial fungi

Answer 22

Aspergillus niger is a fungus which can be used to produce citric acid. Citric acid is commonly used as an acidity regulator in the food and drink industry.

Question 23

Name and describe a harmful fungi

Answer 23

Tricophyton rubrum is a fungus which is a human pathogen, causing athletes foot and ringworm.

Question 24

Name and describe a fungi found on surfaces

Answer 24

Cladosporium halotolerans is a fungi which inhabits damp surfaces as mildew.

Question 25

Name and describe a fungi found in the human body

Answer 25

Tricophyton rubrum is a fungus which is a human pathogen, causing athletes foot and ringworm.

Question 26

Name and describe a fungi found in water

Answer 26

Aspergillus fumigatus is a fungi that can grow in marine enviroments. It is pathogenic and has been known to cause fungal infectons in captive killer whales.

Question 27

Name and describe a fungi found in soil

Answer 27

White rot fungi