Extracellular Matrix

• What is essential for cells to form a multicellular organism?

  Cells must stick to each other
• How are cells and other components organized in tissues?

  They are organized into tissues with extracellular space
• What forms the extracellular matrix (ECM)?

  A network of macromolecules fills the space
• Why are cell adhesion mechanisms and ECM critical?

  They are vital for tissue organization and function
• How do contributions of ECM vary among tissue types?

  They vary significantly across different tissue types
• What are the two extremes of animal tissue organization?

  • Epithelial tissues: tightly bound cells, thin ECM
  • Connective tissues: rich in ECM, few cells
• What characterizes epithelial tissues?

  Sheets of tightly bound cells
• What is the role of connective tissues?

  Provides a route and chemical properties for cells
• How does ECM affect connective tissue properties?

  It determines the tissue's physical properties
• What are the types of connective tissue and their ECM adaptations?

  • Tendon: ropelike, high tensile strength
  • Blood vessel walls: resilient, flexible
  • Cartilage: tensile strength and elastic properties
  • Bone: rigid and incompressible
  • Vitreous content of eye: transparent jelly
• What is the main role of glycosaminoglycan polysaccharide chains (GAGs)?

  They act as space fillers between cells

  
• What are examples of GAGs?

  Heparin sulphate and hyaluronan
• What is the structure of GAGs?

  Unbranched polysaccharide chains with disaccharide units

  
• What is the significance of hyaluronan?

  It attracts water and creates pressure
• What is the main component of proteoglycans?

  Carbohydrate, up to 95% by weight
• What is the main proteoglycan in cartilage?

  Aggrecan
• What is the role of collagens in the ECM?

  They are the major fibrous component
• What percentage of total protein mass in mammals is collagen?

  25%
• How many human genes code for collagen α-chains?

  42 genes
• How do collagen α-chains form a triple helix?

  They wrap around each other in a specific pattern
• What is the role of peptidase in collagen synthesis?

  It cleaves pro-collagen extensions
• What are the types of collagen and their characteristics?

  • Fibril-forming: Bone, skin, tendons
  • Fibril-associated: Cartilage, tendons
  • Network-forming: Basal lamina
  • Anchoring: Beneath stratified squamous epithelia
  • Transmembrane: Hemidesmosomes
• What is the mutant phenotype associated with type 1 collagen?

  Severe bone defects and fractures
• What is the mutant phenotype associated with type 4 collagen?

  Kidney disease and deafness
• What is the mutant phenotype associated with type 9 collagen?

  Osteoarthritis
• What is the mutant phenotype associated with type 17 collagen?

  Skin blistering
• What is the mutant phenotype associated with type 18 collagen?

  Myopia and detached retina
• What is the role of fibril-associated collagens?

  They mediate interactions between fibrils and ECM molecules
• How do fibril-associated collagens differ from fibril-forming collagens?

  They do not form fibrils and are more flexible
• What is the significance of collagen cross-links?

  They stabilize the collagen fibrils in the ECM
• What is the function of the basal lamina?

  It supports and anchors epithelial tissues

  
• What is the role of the ECM in tissue dynamics?

  It influences cell behavior and tissue organization
• How does the structure of collagen contribute to its function?

  Its triple helix provides strength and stability
• What is the importance of proteoglycans in the ECM?

  They act as reservoirs for growth factors
• What is the significance of the repeating unit in GAGs?

  It allows for consistent interaction with cells
• How do collagen trimers self-assemble?

  They form fibrils through covalent cross-links
• What is the role of glycosyl transferases in proteoglycan synthesis?

  They elongate polysaccharide chains in the Golgi
• What is the function of linker proteins in proteoglycan synthesis?

  They connect GAGs to core proteins

  
• What is the role of the secretory pathway in proteoglycan synthesis?

  It transports proteoglycans to the extracellular space
• What is the significance of the high heterogeneity of proteoglycans?

  It allows for diverse functions in the ECM