Chapter 8

• We will explore the structure and function of the cytoskeleton, cell walls, the extracellular matrix, and bacterial cell surface structures

  
• Cytoskeleton


  • Network of cytoplasmic proteins in eukaryotes
• Functions of the cytoskeleton

  • Structural support
  • Cell motility
• Microtubules


  Thick, hollow tubes made of tubulin proteins that twist around each other
• Microfilaments


  Thin, flexible fibres made of actin proteins
• Intermediate Filaments


  Large, stable fibres made of various proteins depending on cell type

  
• Microtubules and microfilaments act as "tracks" for motor protein movement
• Motor proteins


  Drive movement of objects along cytoskeletal filaments by hydrolyzing ATP
• Functions of microtubules


  • Support cell shape
  • Anchor organelles in place
  • Provide pathways for organelle and vesicle movement
  • Separate chromosomes during mitosis
  • Form cilia and flagella

  
• Centrosome


  The microtubule organizing centre of animal cells, where all microtubules grow out from
• Cilia and flagella


  Movement structures made of microtubules, with a 9+2 structure

  
• Dynein


  The motor protein that causes flagellar/ciliar motion by walking along the microtubules

  
• Cilia and flagella have the same structure, but cilia are shorter and more numerous and move fluid across the cell surface, while flagella are longer and fewer and propel the cell forward

  
• Functions of microfilaments


  • Maintain cell shape
  • Facilitate cell division
  • Reshape the cell for phagocytosis and cell crawling
  • Cause cytoplasmic streaming

  
• Functions of intermediate filaments

  • Anchor organelles and nucleus
  • Support cell shape
  • Form nuclear lamina
  • Form desmosomes to connect cells
• Cell walls are always found outside of the cell membrane
• Functions of cell walls

  • Protection against mechanical, chemical, and osmotic damage
  • Give cells their characteristic shape
  • Provide mechanical support
  • Barrier to entry of large molecules
  • Protect from pathogens
  • Mediate cell-cell interactions
• Peptidoglycan


  The polysaccharide and polypeptide network that makes up the bacterial cell wall

  
• Types of bacterial cell walls

  • Gram-negative
  • Gram-positive

  
• Cellulose


  The glucose polymer that makes up the main structural component of plant cell walls

  
• Plasmodesmata are channels through the plant cell walls and membranes that physically connect the cytoplasms of adjacent plant cells

  
• Functions of the extracellular matrix

  • Physical support
  • Adhesion
  • Communication
• Components of the extracellular matrix

  • Collagen
  • Proteoglycans
  • Fibronectin
  • Integrins
• Bacterial capsule


  A sticky layer of polysaccharide outside the bacterial cell wall
• Functions of the bacterial capsule

  • Protection against dehydration
  • Virulence by shielding from immune system and resisting engulfment
  • Adhesion to surfaces
• Bacterial capsules are important for biofilm formation, allowing bacteria to remain in a favourable location and communicate/exchange nutrients and genetic material
• Bacterial flagella


  Structures external to the bacterial cell that are used for movement, powered by a proton gradient
• Endocrine glands include the pituitary gland (located at the base of the brain), thyroid gland (in front of the neck), parathyroids (behind the thyroid), adrenal glands (on top of kidneys), pancreas (partially behind stomach), ovaries/testes (internal sex organs).
• endocrine glands include pituitary, thyroid, parathyroids, adrenal, pancreas, ovaries/testes, pineal body, thymus, hypothalamus
• Hormones are chemical messengers produced by cells or organs, which travel through the blood to target tissues where they bind with specific receptors on cell surfaces.
• hormones are chemical messengers produced by cells or organs, which travel through the blood to target tissues where they bind with receptors on cell surfaces.
• The endocrine system is made up of glands that secrete hormones into the bloodstream.