Extracellular matrix Flashcards
Who invented the first microscope?
Robert Hook
What are the four major types of animal tissues?
Epithelial
Muscular
Nervous
Connective
What are epithelial tissues?
Lining of gut or epidermal layer of skin.
What is on the apical side of epithelial tissues?
Free surface
What is on the basal side of epithelial tissues?
Basal lamina.
Connective tissues.
What are cell junctions?
Link individual cells.
What are the cytoskeleton filaments?
Mechanical forces are transmitted from cell-cell.
What is the basal lamina?
Cells attached to thin layer/mat of connective tissue comprising mostly of ECM.
What is specific about the cells in epithelial tissues?
Asymmetrical/polarised
What are the 4 types of cell junctions found in epithelial tissues?
Adheres junctions: Cadherin
Desmosomes
Tight junctions
Gap junctions
What is cadherin?
Superfamily of Ca+ dependent molecules with many distinct classical and non-classical members.
It is homophilic.
What is the structure of adherens junctions?
Transmembrane spanning molecules.
Has an extracellular and transmembrane region as well as a cytoplasmic region.
They span half the distance between the cell.
What is the function of cadherin mediated cell junctions?
Provide structural strength.
Organisation as cadherin can only interact with itself.
How does cadherin mediate cell junctions?
In the presence of Ca2+, the vinculin attaches to the alpha-catenin causing it to go from folded to extended, as it moves the actin filament allowing the myosin II to pull on it.
What is RAC?
Small gTP-binding protein involved in regulating actin cytoskeleton, the activated form of RAC seems to induce membrane ruffling.
What is RHO?
A member of ATP-dependent hexameric helicases that function by wrapping nucleic acids around a single cleft extending around the entire hexamer.
What is the function of RAC on cadherin mediate cell junctions?
Regulates aherens junction assembly.
What are desmosomes?
Similar to adherens junctions but contain specialized cadherins that connect with intermediate filaments, allow junctions to have strength.
Considered a molecular zip.
What are tight junctions?
Epithelial tissues which act as a selective permeability barrier this adds functional ability to membranes.
How are tight junctions investigated?
Using tracer molecules, however tracer molecules can’t get through.
What are gap junctions?
Channels made from connexins and innexins.
Allows only very tiny molecules.
What is the function of the tight junction?
Seals neighbouring cells together in an epithelial sheet to prevent leakage of extracellular molecules between them; helps polarize cells.
What is the function of adherens junctions?
Joins an actin bundle in one cell to a similar bundle in a neighbouring cell.
What is the function of desmosomes?
Joins the intermediate filaments in one cell to those in a neighbour.
What is the function of a gap junctions?
Forms channel that allow small, intracellular water-soluble molecules, including inorganic ions and metabolites, to pass from cell to cell.
What is the ECM?
Extracellular matrix.
What is the extracellular matrix?
ECM is the main stress-bearing component of connective tissue and forms an indirect means of cell-cell contact.
What are the functions of the ECM?
Support and strength
Cellular communication
Cell migration, polarity and shape.
What is the basal lamina?
Very thin layer of ECM produced by cells above and below.
What is the function of the basal lamina?
Essential for maintaining epithelial tissues.
What is the basal lamina composed of?
Laminin
Type IV
XVIII collagen
Nidogen
Perlecan fibronectin
What are the two different types of cells found in connective tissue?
Indigenous
Immigrant
What kinds of indigenous connective tissues cells are there?
Primitive mesenchymal cells
Specialized cells
What are primitive mesenchymal cells?
Undifferentiated cells that can lead to the generation of other connective tissue cell, fat cells (adipocytes), mast cells (release histamine) and fibroblasts.
What are fibroblasts?
Found in many connective tissues and
synthesize most of the molecules found in the ECM.
What kinds of specialized cells are there in the connective tissues?
Adipocytes
Mast cells
Chondrocytes
Osteoblasts
What kind of immigrant cells are present in connective tissues?
Immune cells.
What is the composition of connective tissue EMC?
- GAGs
- fibrous proteins
- glycoproteins
What are GAGs?
Consist of repeating sulphated disaccharide units.
Most anionic molecules produced by animals.
Often linked to form proteoglycans.
What are fibrous protein?
Members of collagen family.
Most abundant proteins in mammals.
What is the structure of fibrous proteins?
Long, stiff triple stranded helical structure.
What is the function of fibrous proteins?
Provides tensile (pulling) strength of tissues.
What is the collagen family of proteins?
Synthesized by indigenous ECM cells.
40 different types
3 polypeptides form a coil different a chain combinations lead to different types of collagen (Type I- XVIII) found in differing connective tissues.
What is collagen?
3 polypeptides form a coil, which can then self-aggregate into fibrils and then fibres.
What is the organisation of collagen strands?
- Single collagen polypeptide chain.
- Triple-stranded collagen molecule
- Collagen fibril
- Collagen fibres
What is procollagen?
Soluble precursor of tropocollagen formed by fibroblasts and other cells in the process of collagen synthesis.
What is the function of procollagen?
Procollagen prevents aggregation inside cells
What is the process of procollagen becoming a collagen molecule?
Procollagen is secreted from secretory vesicle.
Procollagen proteinase cleaves terminal procollagen extension.
What types of glycoproteins are present in the ECM?
Elastins
Fibronectins
What are elastins?
Provide elasticity to connective tissue (similar in structure to collagen).
Dominant component of the ECM in arteries.
What is fibronectins?
Bind other matrix/cell membrane proteins organize matrix and provide cell-matrix link.
What are integrins?
Key receptors that bind ECM components.
Alpha and beta chain large N-terminal domain.
Short intracellular domain that binds adapters similar to those seen with cadherins.
What ligands do a5B1 bind?
Fibronectin
What ligand do a6B1 bind?
Laminin
What ligand do a7B1 bind?
Laminin
What ligand do aLB2 bind?
Ig superfamily counterreceptors
What ligand do aHbB3 bind?
Fibrinogen
What ligand do a6B4?
Laminin
What is the distribution of a5B1 receptors?
Ubiquitous
What is the distribution of a6B1 receptors?
Ubiquitous
What is the distribution of a7B1 receptors?
Muscle
What is the distribution of aLB2 receptors?
White blood cells
What is the distribution of aHbB3 receptors?
Platelets
What is the distribution of a6B4 receptors?
Hemidesmosomes in epithelia