Long Quiz 3

• Turgor Pressure - hydrostatic pressure exerted by the cytoplasm against the cell wall due to water influx.
• Osmotic pressure - difference in concentration of solutes (salts and sugars) between the cytoplasm and surrounding environment, driving water influx.
• Fungal cell wall - a dynamic structure composed of various polymers and proteins, providing structural support and resisting expansion.
• Functions of a fungal cell wall

  • Maintains cell shape.
  • Protects from harmful substances.
  • Mediates nutrient absorption.
  • Adhesion
• Variation in the Fungal Cell wall: proportions of chitin, glucans, and proteins varies between fungal species
• The Fungal cell wall is composed of Stress-bearing polymers and Cell wall proteins (CWPs)
• Beta-1 to 3-glucan is the most abundant polymer in most fungal species
• Chitin synthase - enzyme that extrudes chitin chains through the plasma membrane for microfibril formation.
• Chitosan - secondary support to chitin
• Ergosterol - Exclusive to fungi, it maintains membrane fluidity and permeability.
• Integral polytopic proteins - aka transmembrane proteins, they are involved in ion/molecule transport
• Integral monotopic proteins - embedded in only one side of the membrane
• The Fungal plasma membrane is composed of lipids, ergosterol, and membrane proteins
• Fungal plasma membrane is responsible for Ion transport
• Symporters - carrier proteins that couple the influx of protons with the import of specific molecules
• Antiporters - carrier proteins that couple the influx of a proton (or other ion) with the export of a different ion or molecule
• Carrier proteins - integral membrane proteins that facilitate secondary active transport
• Secondary active transport - utilizes the electrochemical gradient to drive the transport of other molecules against their concentration gradient.
• Fungal Endomembrane system - supports growth and development through secretory and endocytotic pathways.
• The Fungal endomembrane system is composed of the Endoplasmic reticulum, Golgi apparatus, Vacuoles, and Vesicles
• Fungal Golgi is dispersed and lacks the stacked cisternae seen in animals and plants.
• Fungal cytoskeleton - maintains cell shape and directs organelle trafficking within the cell
• The fungal cytoskeleton is composed of actin microfilaments, microtubules, and septins
• Actin microfilaments - interact with actin-binding proteins to form cables, patches, and rings
• Microtubules - hollow tubes formed by α-tubulin and β-tubulin monomers. It is involved in. Organelle transport, nuclear positioning, and mitotic spindle formation and chromosome separation.
• Septins - GTPase proteins that form rods, filaments, and sheets.
• Spitzenkorper - described as the organizing center for hyphal growth and morphogenesis in fungi. It is Located at the growing tip of hyphae and involved in spore germination and branch formation.
• In non-septate fungi like zygomycetes, hyphal extension creates continuous, multinucleate networks
• In septate fungi, hyphal tip grows and branches with septa formation. Number of nuclei per compartment varies between groups.
• Spore germination - involves the emergence of a young hypha, or germ tube, followed by continuous elongation and branching.
• Anastomoses - site where fungal hyphae merges with another in basidiomycetes and ascomycetes; hyphal fusion. This is for the purpose of resource sharing.
• Appressorium - inflated cells produced by plant pathogens, it is the point of contact as it penetrates the plant tissue
• Haustorium - nutrient absorbing structures that lives inside the plant cell. It is connected to the appressorium.
• Arbuscules - nutrient absorbing structures that lives inside the root cells. It is produced by Glomeromycota
• Some bacterial cells use hyphae channels to get to nutrient sources
• Strands - simple bundles of hyphae with adhering cell walls
• Cords - linear organs without an organized tip
• Rhizomorphs - larger invasive organs that have an identifiable tip that pushes through the soil
• Sclerotia - hardened masses of hyphae that serve as survival structures for ascomycetes and basidiomycetes
• Hydrophobins - small cysteine-rich, water repellant proteins that are secreted on the surface of aerial hyphae and fruit bodies