Fungi & Cell Types – Exam Review

Cell Types: Prokaryotes vs Eukaryotes

  • Prokaryotes: simple, \text{\small} size, no nucleus, no membrane-bound organelles, peptidoglycan cell wall, small ribosomes; examples: Bacteria, Archaea
  • Eukaryotes: complex, \text{\large} size, true nucleus, membrane-bound organelles, chitin/cellulose cell wall (plants, fungi), large ribosomes; include Protists, Fungi, Plants, Animals
  • Shared features: DNA, ribosomes, cytoplasm, plasma membrane

Eukaryotic Cell Organelles (keywords)

  • Nucleus, nucleolus, nuclear envelope & pores
  • Endoplasmic reticulum (smooth & rough)
  • Golgi body, lysosome, peroxisome, vesicles
  • Mitochondrion, cytoskeleton (microtubules, centrioles), ribosomes
  • Plasma membrane, cytosol, flagellum

Fungi Overview

  • Forms: yeast (unicellular), mold (multicellular hyphae/mycelia), mushrooms (multicellular fruiting bodies)
  • Cell wall mainly chitin; membrane sterol = ergosterol
  • Chemoorganoheterotrophs; glycogen storage; mostly aerobic, some facultative/strict anaerobes

Fungal Structure

  • Hyphae: septate (cross-walls) or coenocytic (>1 nucleus)
  • Mycelium: compact tuft of hyphae (mold)
  • Aerial hyphae produce conidia (asexual spores); pigmented & desiccation-resistant
  • Cell-wall polymers: mannoprotein, \beta-glucan, chitin

Fungal Reproduction

• Asexual (predominant)

  • Fragmentation of hyphae → arthroconidia
  • Fission, budding (yeasts)
  • Spore types: conidiospores, sporangiospores, chlamydospores, blastospores
    • Sexual (genetic variation)
  • Fusion of two haploid nuclei → diploid → meiosis
  • Sexual spores: ascospores, basidiospores, zygospores

Symbiotic Associations

  • Mycorrhizae: fungus + plant roots (water/mineral uptake ↔ sugars)
  • Lichens: fungus + algae/cyanobacteria (moisture/shelter ↔ photosynthate)
  • Gut symbionts in ruminants; fungal “farms” by ants/termites

Pathogenic & Toxic Roles

  • Plant diseases: corn smut, tar spot, ergot
  • Animal mycoses: blastomycosis, candidiasis, coccidioidomycosis, histoplasmosis, sporotrichosis, paracoccidioidomycosis
  • Mycotoxins: aflatoxins (Aspergillus), ergot alkaloids (Claviceps), amanitins (Amanita); effects on livestock/humans
  • Food spoilage: natural decomposers of organic matter

Industrial & Biotechnological Importance

  • Food & beverage: bread, cheese, alcoholic drinks (Saccharomyces, Penicillium)
  • Pharmaceuticals: antibiotics (Penicillium → penicillin), recombinant proteins (insulin-like factors)
  • Biocontrol: Beauveria bassiana vs dengue mosquitoes; Cordyceps vs insects

Key Takeaways

  • Fungi are chitin-walled eukaryotes that can be unicellular or multicellular.
  • They reproduce mainly asexually but also sexually, generating diverse spore types.
  • Roles range from decomposition, symbiosis, and industry to disease and toxin production.