Fungi

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  • Created by: LBCW0502
  • Created on: 12-02-20 13:36
Describe features of fungi (1)
Defined group of micro-organisms. Reproduction is used to classify various fungi. Fungi are recognised as agents of diseases in humans
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Describe features of fungi (2)
Eukaryotes, more like human cells (influences fungal treatments – want selective drug toxicity, kill fungi and not affect human cells). Bacteria/prokaryotes (less like human cells). Fungi have similar biochemistry to human cells
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Describe features of fungi (3)
Difficult to find selective drug toxicity targets. Small section in BNF for antifungals (have more antibiotics/antivirals compared to antifungals). Lack of movement in antifungals (only change in formulation)
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Describe features of fungi (4)
Lack of movement in antifungals (only change in formulation). Dimorphism. Need to understand morphology of fungi – determine if they are commensal or pathogenic, dimorphic shift
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Describe features of the phylogeny of Eumycota
Fungi closely related with plants and animals (eukaryotic). Fungi are not plants (differ in key ways, no differentiated stems/roots/leaves/flowers, fungi are not photosynthetic). Fungi live on dead decayed matter. Saprophytes
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Why study fungi? (1)
Fungi can cause disease in other organisms as well as humans e.g. fruits, crops (finding source of reduced carbon). Penicillin – first isolated from surface of oranges. Mushroom/fruiting body, fungus in soil. Formation of spores – spread of fungus
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Why study fungi? (2)
Recycling elements – C, N P in the environment (cycling of nutrients in the environment). Antibiotics – penicillin/beta-lactams.
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Why study fungi? (3)
Fungi used in biochemical experiments, eukaryotes, similar to humans, used to understand human biochemistry e.g. cancer, cell cycle of fungi. Biotechnology - use of fungi
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Why study fungi? (4)
Fungus would be better to produce proteins compared to E.coli (more similar to human cells, protein folding, post-translation modifications of peptide, may not happen in bacteria/prokaryotes)
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What are the basic fungal forms? (1)
Yeast type – binary fission or budding to reproduce
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What are the basic fungal forms? (2)
Hyphae/filamentous form – produces a filament, smaller than human hair (microscopic), filaments form mats of interconnecting filaments (mycelium), increase area to secrete digestive enzymes across substrate, larger SA,
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What are the basic fungal forms? (3)
More substrate can be broken down and utilised by hyphae, grow from apical tip, colonising new substrates, use up substrate in one area, colonise another area to find nutrients
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What are the basic fungal forms? (4)
Uses up substrate in centre of mat – grows upwards into atmosphere (reproduction), aerial filaments
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What is apical dominance?
Apical dominance – cells differentiate into spores (advantage – more likely to spread)
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What are the two reproductive cycles in fungi?
Sexual (sexual reproduction – large groups of fungi) and asexual spores
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Describe features of the types of asexual spores (1)
Asexual spores – different morphologies, used characteristically to identify spores at species level
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Describe features of the types of asexual spores (2)
Important medically – could be allergens, induce hypersensitivity reaction, spores spread through the air, can be inhaled (spores germinate in moist respiratory environment e.g. pulmonary infection)
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Describe features of the types of asexual spores (3)
Filamentous forms (fungi) – mould types
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Describe features of fungal classification (1)
Four divisions based on the type of sexual reproduction. Zygomycota, ascomycota, basidiomycota, deuteromycota (fungi imperfecti – for fungi which cannot be identified in both sexual/asexual forms)
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Describe features of fungal classification (2)
Identify sexual and asexual stages to incorporate into a division – can have the same fungus in two different forms
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Describe features of the zygomycetes (1)
Zygomycetes e.g. mouldy bread, not interested in disease for this division but important in biotechnology (depraprovira) – due to products being produced
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Describe features of the zygomycetes (2)
Nutrients depleted – aerial mycelium formed, spores formed (enclosed within a sac, released when matured) – asexual stage (mitotic division)
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Describe features of the zygomycetes (3)
Two hyphae can interact with each other – can join (sexual stage), different mating types (+/-), fusion of hyphae of different mating types. Nuclei from each of the hyphae will fuse to form zygote
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Describe features of the zygomycetes (4)
Hyphae filament to form mycelium mat – many nuclei, multi-nucleated. Pore through sceptre to allow movement of nutrients and nuclei
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Describe features of the zygomycetes (5)
Haploids become diploid to form zygote. Meiosis occurs – reduce chromosome number to haploid stage, release spores. Zygote spore forming
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Describe features of ascomycetes
E.g. truffle, history of ascomycetes (Salem's Witch Trials, Alexander Fleming – observed anti-microbial effect of penicillin).
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Describe features of the sexual cycle of ascomycetes (1)
Fusion of two different mating types, fusion of hyphae, mating between different nuclei, form a dikaryon, meiosis, septation, division, remain with eight spores (eight nuclei) within a sac – characteristic, ascus, ascospore,
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Describe features of the sexual cycle of ascomycetes (2)
Many of aerial hyphae to form a fruiting body for dispersion
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Describe the sexual cycle of the basidiomycetes (1)
Fusion of different mating types of hyphae, dikaryotic mycelium, spore structures come together to form different budding effects, gives a stalk and fruiting body (mushroom), under gills (spore carrying structure – basidium)
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Describe the sexual cycle of the basidiomycetes (2)
Pizza mushroom. Magic mushroom (class A drug). Fallen angel – produces hepatotoxin (dangerous with alcohol)
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Which feature distinguishes the fungi between the different divisions?
Release structure for each division is different (spores, haploid stage)
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Describe features of medical mycology (selective drug toxicity) - 1
Fungal cell wall consists of predominantly chitin (humans have no cell wall). N-acetylglucosamine (monomers in peptidoglycan)
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Describe features of medical mycology (selective drug toxicity) - 2
Fungal cell membranes contain sterols (cholesterol in humans – fluidity of cell membranes), fluidity of cell membranes. Dimorphism – many fungi can interchange between the two forms (oxygen tension, nutrient availability etc – cause shift)
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Describe features of medical mycology (selective drug toxicity) - 3
Infections can be cutaneous, subcutaneous, systemic or opportunistic
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Describe features of cutaneous mycoses
Fungi on keratinised structures of the skin (not-living), epidermal layer, nail plate, fungi can break down keratin (used as carbon source). E.g. ringworm, athlete’s foot (with secondary bacterial infection), fungal infection of nail plate
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Describe features of subcutaneous mycoses
Subcutaneous – fungi trapped in SC layer, draining sinuses.
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Describe features of systemic mycoses (1)
Systemic mycoses – fungi spreads through the body, usually in a unicellular yeast form (easier to pass through lymphatic capillary systems), make cytoskeleton rearrangement e.g. Candida albicans
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Describe features of systemic mycoses (2)
Fungi trapped in small capillaries, inflammatory response. Can act as allergens – hypersensitivity reactions, systemic infection. Vast majority of fungi handled by immune system
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Why are the number of cases for fungal infection increasing?
Due to changes in medical practice, more people immunocompromised, more people die of infection (rather than cancer – chemotherapy), number of transplants have increased/use of immunosuppressants
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Describe features of opportunistic fungi
Oral candida albicans (thrush) infection, in yeast form, typical sign of immunosuppression leading to secondary infection, pathogenic, white plaques form on mucosal surface
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Card 2

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Describe features of fungi (2)

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Eukaryotes, more like human cells (influences fungal treatments – want selective drug toxicity, kill fungi and not affect human cells). Bacteria/prokaryotes (less like human cells). Fungi have similar biochemistry to human cells

Card 3

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Describe features of fungi (3)

Back

Preview of the front of card 3

Card 4

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Describe features of fungi (4)

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Preview of the front of card 4

Card 5

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Describe features of the phylogeny of Eumycota

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