Fungi Flashcards
(27 cards)
Fungi can be broadly split into ____ groups. The groups are _____. Some fungi are said to be ____ as they can ____.
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.
The major components of fungal structure are _____ (7 answers)
- The cell wall 2. Chitin
- Hyphae 4. Mycellium
- Septum 6. Coenocytic hyphae
- Woronin bodies
Describe the fungal cell wall
The cell wall of a fungi consists of chitin ( a major polysacharide component) and β-glucans. It also contains hydrophobins that repel water.
Explain the term Chitin.
Chitins are major polysacharide component found in the cell wall of most fungi.
Describe hyphae generally and mention it’s sub-types.
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.
State the functions of 1. Vegetative hyphae and 2. Reproductive hyphae
- Vegetative hyphae form mycelia and enable the fungus to obtain nutrients from it’s enviroment whilst anchoring it in it’s substrate
- Reproductive hyphae form reproductive spores.
Describe the different septa which appear in septate hyphae.
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.
What are the names given to hyphae which do not form septa?
Aseptate or coenocytic
Explain what is meant by Woronin bodies.
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.
Explain the term coenocytic hyphae.
Coenocytic or aseptate hyphae are hyphae which are not compartmentalized by septa.
What is meant by mycellium?
Mycellium is a term for a mass of hyphae
What is the optimal temperature range for mesophillic fungi?
15C to 30C
What is meant by Saprotrophs
Saprotrophs describe an organism (in this case a fungus) which obtains it’s nutrients from decaying organic matter.
Explain the process by which saprotrophs obtain nutrients.
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.
Explain the following terms
- Xerotolerant fungi
- Fungistatic
- Fungicidal
- Fungus which can grow in low water enviroments
- An agent which can prevent the growth of fungi without necessarily killing the fungi
- An agent which kills fungi and prevetns the growth of further fungi.
Describe the characteristics of a zygomycota
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.
Describe asexual reproduction in zygomycetes.
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.
Describe sexual reproduction in zygomycetes.
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.
Describe asexual reproduction in ascomycotes.
Haploid spores called conidia form via mitosis on the end of an aerial hyphae called a conidiophore
Describe sexual reproduction in ascomytcetes.
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.
Name and describe a beneficial fungi
Penicillium chrysogenum produces penicillin as a secondary metabolite. The penicillin can then be purified and administered as an anti-bioteic to fight bacteial infection.
Name and describe an indirectly beneficial fungi
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.
Name and describe a harmful fungi
Tricophyton rubrum is a fungus which is a human pathogen, causing athletes foot and ringworm.
Name and describe a fungi found on surfaces
Cladosporium halotolerans is a fungi which inhabits damp surfaces as mildew.
