ECM and cell junctions Flashcards
??? refers to the biological structures at the interface between cells with different types that govern tissue structure and functioning
junctions
junctions are critical for maintaining ??? integrity of cells as well as permeability and communication
structural integrity
What is the extracellular matrix?
it is the scaffold of molecules within a tissue that surrounds and provides structural support to cells
what is critical for mechanical support of cells, cell behaviour and tissue repair?
the extracellular matrix
??? mediates cell to ECM interactions
integrins
??? refers to the biomolecular components that exist within tissues but outside cells as an organised network of material beyond the cell plasma membrane
the extracellular matrix
the composition of the ECM varies in different tissue types but typically is composed of ??? and polysaccharides
proteins
with what type of membrane-spanning proteins are cells connected to the ECM?
integrins
what are the two main forms of ECM?
basement membrane (aka basal lamina) and connective tissue
which one- the basement membrane or connective tissue- is a continuous layer providing specialised, supportive foundation for epithelial and endothelial cells?
basement membrane
which one- the basement membrane or connective tissue- surrounds muscle and fat cells to provide mechanical support and separates tissue/organs and enables cell migration?
basement membrane
which one- the basement membrane or connective tissue- is far more structurally diverse and includes dermis, cartilage, tendons, bone, teeth, cornea, mollusc shells, plant and fungal cell walls, etc?
connective tissue
the three classes of ECM molecules are:
1. ??? proteins
2. Adhesive glycoproteins
3. proteoglycans with GAGs
- Fibrous proteins
which class of ECM provides strength, elasticity and rigidity to tissues, with collagen being the most common type of ECM molecule in this class?
Fibrous protein
which class of ECM includes laminin and fibronectin (a glycoprotein that is post-translationally modified by addition of carbohydrates and facilitates adhesion between cells and ECM by attaching integrins to elastin or collagen)
adhesive glycoproteins
ECM Class 3 Proteoglycans with GAGs consist of a core protein with ??? attached GAG chain
covalently
ECM Class 3 Proteoglycans with GAGs have an increased or decreased negative charge due to sulphated GAGs binding cations which attracts water molecules = hydrated gel that fills extracellular space
increased
Integrins are ??? proteins that span entire plasma membrane: Extracellular domain which binds to fibronectin with an internal domain that binds indirectly to actin
receptor proteins
integrins provide mechanical resistance but also mediate ???
cell signalling
the external and internal signals from environment cause conformational changes in ??? which changes or influences binding behaviour
integrins
when integrins are in bent or extended state (?) they are active
extended state
when integrins are in bent or extended state (?) they are inactive
bent
integrins bind to ??? which bind to collagen
fibronectin
TRUE or FALSE: A tight junction seals neighbouring cells together in an epithelial sheet to prevent movement of substances between cells
TRUE
what type of junction causes cell to cell anchoring, tying together two cells via actin molecules of each cell and are mediated by cadherins?
adherens junction
Desmosomes interact with ??? filaments of adjacent cells and are mediated by cadherins
intermediate filaments
Gap junctions allow direct or indirect transfer of material such as small water molecules and ions between the cytoplasm of adjacent cells?
direct transfer.
what is the role of hemidesmosomes?
cell matrix anchoring
which type of junction is critical in maintaining selective permeability so that only certain molecules can be absorbed through via dedicated processes such as channels (i.e BBB)? Gap or Tight junctions?
tight junctions
TRUE or FALSE tight junctions maintain polarity and asymmetry of a cell. e.g. in epithelia one side faces lumen (external environment) = apical, whilst the other side faces underlying tissue (internal environment) = basolateral. also ensures certain receptors are confined to apical or basolateral space
TRUE
Cadherins bind together cells via their ??? e.g. in adherens junctions, cadherins bind to actin whilst in desmosomes they bind intermediate filaments
cytoskeletons
do integrins or cadherins require Ca2+ for binding and typically mediate homophilic (same cells) binding?
cadherins
which type of junctions is predominantly made with connexons and provide direct channels that traverse membranes of adjacent animal cells?
Gap junctions
connexons are 6 subunits of ??? proteins
connexin
are hemidesmosomes integrin or cadherin mediated? they bind to basal lamina via cytoskeleton, e.g. keratin
integrin
do gap junctions or desmosomes allow water soluble molecules ~1000 Da to move directly from cytosol of one cell to the next, enabling electrical and metabolic coupling of cells? e.g cardiac tissue
gap junctions
TRUE or FALSE: gap junctions can be opened or closed as needed in response to extracellular signals
TRUE
In the case of basal lamina, which has an incontinous membrane that supports cells above it, hemidesmosomes ??? the cells to membrane
anchor
What type of junction ensures certain receptors, channels etc. are
confined to the apical or basolateral space?
Tight junctions
