Cell junctions Flashcards
what are the three types of interactions between cell junctions
occluding junctions
anchoring junctions
communicating junctions
what is the main function of occluding junctions
seal cells of a epithelium, preventing small molecules leaking from one side to the other
what are the two types of occluding junctions
tight and septate (in insects)
what does formation of occluded junctions lead to
provides selectively permeable membranes
what two sides do polarised cells have
apical and basal
describe transport proteins in relation to occluding junctions
different transport protiens at different locations
describe the seal of occluded junctions
not absolute, controllable (important for aa and small sugars)
what is a component of epithelial cells
epi villi
what are epi-villi
they increase surface area
what is the function of epithelial cells
specialised proteins that pump molecules across membranes - up conc gradient
describe the composition of tight junctions
row of opposing transmembrane echesion proteins
name two transmembrane adhesion proteins
claudins and occodin
what are anchoring junctions
mechanically attach cells to other cells or to the matrix
describe the two actin filament attacthcment sites
cell-cell junctions (demosomes)
cell-matrix junctions (hemidesmosomes)
where are anchoring junctions found
in tissues that have mechanical stress- heart, muscle, epidermis etc
what do desmosomes do
adhere junctions
hold cells together using transmembran eproteins and cadherins
what do hemidesmosomes do
focal ahesions
bind to extracellular matrix using transmembrane proteins, integrins
describe a commonality between desmosomes and hemidesomosomes
both have intracellular anchoring proteins that connect junction to cytoskeleton
what are two examples of adheres junctions of cell-cell actin filaments
various forms but adhesion belts in epithelial cells
where is the location of adheres junctions cell-cell actin filaments
below the tight junctions encircling the cell and form before tight junctions
