Fungi Flashcards
Layers of Fungi Cell Wall
Chitin is right above plasma membrane. Beta 1,3 glucan and then Beta 1,6 glucan woven together on top of chitin. Upper layer of glycoproteins and polysaccharides.
What percent of cell wall is polysaccharides
80-90%
Cell Membrane
Cell membrane similar to animal and plant cells - has ergosterol (6% of membrane composition) rather than cholesterol
It allows regulation of osmotic pressure and good in varying environments.
Evolutionary advantage - ergosterol is seen in all fungi
3 types of Fungi
Yeast
Moulds/Mycelial
Mushrooms
Fungi are heterotrophic - they are either
Saprophytic - feed of dead organic matter
Or
Parasitic - lives inside or outside alive host
Yeasts size
3 -30um
Yeast shape and cell organisation
Spherical, oval and cylindrical
Unicellular
Reproduction
Sexually - spores
Asexually - Budding
Mould structure
Filamentous - they have large branched/thread like filaments called hyphae. Hyphae become compacted to form mycelium.
Mould nuclei
Hyphae have many nuclei due to many cells interconnecting to form the hyphae
Septate Hyphae
Have septums seperating each cell. Large pores between each septum so cell contents can be exchanged easily
Coenocytic Hyphae
They have no septums between cells and contents are free to move through a huge combined cytoplasm
Mushrooms
Fruiting body of the mushroom and only grows when conditions are perfect. Mycelium grows under ground and provides it with water. They release the spores into the surrounding area
Life span of mushroom vs mycelium
Mushroom is short lived but mycelium can survive underground for a long time
Dimorphism
Fungi can change from being a yeast to being a mycelium. This is due to temperature. Mycelium in the cold and yeast in the warmth
Fungi can reproduce…
Sexually or asexually. It depends on the environment/condition that the fungi is in. Both are used.
Yeast Asexually Reproduction - what is fission?
Fission is when all cell contents are replicated and the cell membrane divides in two forming two cells.
Yeast asexual reproduction - what is budding?
Cell contents are replicated but bud grows on side of parent cell and then breaks away - it is not completely mature so is smaller than parent cell. A fungi cell can bud many times.
What is vegetative hyphae in mould?
Hyphae grow under the surface like roots to find nutrients and expanding the area which the mycelium covers
Aerial hyphae?
Grow above the growth surface to spread spores to the environment. They release condiospores or sporangiospores
Sexual Reproduction - Moulds
Fusion of unicellular gametes or specialised hyphae or fusion of two haploid cells.
3 steps of sexual reproduction in moulds
Plasmogamy - fusion of cytoplasm
Karyogamy - fusion of nuclei to form diploid cells
Meiosis - to produce haploid spores
Ascospores form in inclosed sac and basidiospores form in club shaped structure.
Moulds use?
Yeasts use?
Mushrooms use?
Moulds use both methods
Mushrooms use basidiospores
Yeast uses ascospores
Importance of fungi?
Industrial use - fermentation and genetic engineering
Medical use - colonisation of fungi in body can cause disease. Some people are allergic to their spores and they may release toxins
Mycoses
Is an infection caused by a fungi
Superficial infection?
Only surface layers of the body are affected - athletes foot
What are Subcutaneous infections - why are they difficult to treat?
Colonisation of fungi at deeper layers of the skin - difficult to treat as drugs do not easily penetrate the skin
Systemic Infections
Fungus is able to colonise and grow in internal organs. Primary pathogens infect person directly and spread infection to many organs which can be fatal. Primary pathogens are often dimorphic.
Secondary pathogens only attack people with low immunity.
Candida Infections
Yeast infection - superficial infections include oral or vaginal thrush and systemic infections include candidemia which is infection of the blood. People with low immunities are at high risk
Treatment - antifungals are difficult to produce as fungi cella have similar structure to human cells so can be dangerous. What are the 3 types of ergosterol inhibitors known?
Polyenes - they bind to ergosterol and disrupts membrane function - nystatin
Azoles - inhibit enzyme that is involved in production of ergosterol - canesten, clotrimazole
Allylamines - inhibit other enzyme that produces ergosterol - terbinafine
