Exam 3 Review

Exam 3 Review - Chapter 31 Fungi Exoenzymes hydrolytic...

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Chapter 31- Fungi Exoenzymes – hydrolytic enzyme secreted by fungus outside of body to digest food Hyphae – filaments composed of tubular cell walls Chitin – contained in fungal cell walls (strong but flexible nitrogen polysaccharide) Mycelium – densely branched network of hyphae, surrounds and infiltrates the material on which fungus feeds; maximizes surface area for nutrient absorption; fungus uses energy to grow rapidly by adding hyphal length; usually subterranean Septa – cross-walls that divide hyphae into cells; have pores for ribosomes, mitochondria, and nuclei to flow from cell to cell Coenocytic – non-septate hyphae; multinucleated cytoplasmic mass (from division of nuclei without cytoplasmic division) Haustoria – specialized hyphae that can penetrate host tissue in parasitic fungi Sexual Reproduction – plasmogamy, karyogamy, meiosis o Plasmogamy – fusion of cytoplasm of two parent mycelia (part of syngamy) o Heterokaryon – different nuclei from each parent coexist (after plasmogamy, before karyogamy); can be mosaic or mingle o Dikaryotic – two haploid nuclei per cell (one from each parent) o Karyogamy – haploid nuclei from parents fuse, producing diploid cells (only diploid stage of fungus) Chytridiomycotes (chytrids) – flagellated zoospores, coenocytic hyphae Zygomycota (zygote fungi) – responsible for bread and produce mold; diploid zygosporangium resistant to freezing and drying, germinate when conditions improve Glomeromycota – form arbuscular mycorrhizae w/ plants (endomycorrhizae); treelike arbuscule; only reproduce asexually by blastospores Ascomycota (sac fungi) – largest group, all yeasts and mildews o Ascospores – sexual spores o Asci – produce 8 ascospores o Ascocarp – fruiting body; contain asci o Conidia – asexual spores o Conidiophores – conidia are produced externally at the tips of these hyphae Basidiomycota (club fungi) – important wood decomposers o Basidium – dikaryotic, line basidiocarp gills, release basidiospores o Basidiospores – sexual spores o Basidiocarp – fruiting body (mushroom) Deuteromycetes – “imperfect fungi”; no known sexual stage; mold
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Lichens – symbiotic; hyphae + green aglae/cyanobacteria; algae provide carbon/fix nitrogen, fungi provide suitable environment o Soredia – for asexual reproduction Mycosis – fungal infection (when fungi parasitizes animal) Mycorrhizae – mutually beneficial relationship between fungi and plant roots; fungi deliver phosphate ions and other minerals to plants, which supplies fungi with organic nutrients o Ectomycorrhizal – form hyphae over root surface and in extracellular spaces o Endomycorrhizal – hyphae through root cell wall Absorptive mode of nutrition – secrete exoenzymes into surroundings which break down complex molecules into organic compounds that fungi can absorb o Saprobes – break down and absorb nutrients from nonliving organic matter
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This note was uploaded on 08/25/2008 for the course BIOL 112 taught by Professor Vaughn during the Spring '08 term at Texas A&M.

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Exam 3 Review - Chapter 31 Fungi Exoenzymes hydrolytic...

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