Cell Junctions Flashcards
What 5 things are cell junctions essential for?
maintaining positions with the body
giving strength to the tissues
cell-cell communication (signalling)
ECM-cell signalling (info about environment)
sharing of cytoplasm between neighbouring cells
What does the structure of a cell junction depend on?
function and environment
what are the 6 types of cell junctions?
tight junctions
gap junctions
plasmodesmata
adherens junctions
desmosomes
hemidesmosomes
Where do tight junctions form?
at the apex of animal cells between neighbouring epithelial cell
What type of cells have tight junctions and where?
at the apex of animal epithelial cells
What is the purpose of tight junctions?
they form a water-tight barrier between compartments
How do tight junctions form on the cell?
as a series of pockets in a belt around the cell
What are the series of pockets made by tight junctions?
intercellular spaces each surrounded by a network of proteins
What do tight junctions prevent?
the movement of molecules between cells (paracellular movement) and make it so that only transcellular pathways are available
What is an analogy for tight junctions?
gaskets or belts
Describe the structure of tight junctions
the integral proteins of tight junctions form continuous fibrils that encircle the cell like a gasket to prevent paracellular movement of molecules between epithelial animal cells
What do the integral proteins of tight junctions make contact with?
the neighbouring cells on all sides
What are the two families of proteins important to tight junctions?
claudins and occludins
What type of cell junction is essential in forming the blood/brain barrier?
tight junctions in endothelial cells of the blood vessels in the brain
T or F: most capillaries do not have tight junctions
true except the ones in endothelial cells in blood vessels of the brain
What is the purpose of the tight junctions in the blood/brain barrier?
it prevents the passage of molecules into the brain such as ions and water
What can still get through the blood brain barrier? Why?
immune cells can send out protein ligands that interact with the tight junction complexes and open them
T or F: tight junctions also maintain structural polarity of epithelial cells
True
How do tight junctions help maintain the structural polarity of epithelial cells?
the thick band keeps apical membrane proteins from moving too far down the sides of the cells aaand it keeps basolateral membrane proteins from reaching the apical side
What is the zonula occludens?
the band of tight junctions around epithelial cells
Describe gap junctions
sites of communication between adjoining animal cells
What is the function of gap junctions?
intercellular communication
exchange of materials between the two cells
T or F: gap junction proteins in 2 cells are not attached
false they are attached to allow intercellular communication and exchange materials between them
Are gap junctions in animal cells or plant cells?
animal cells