Module 3: Lesson 6 Flashcards
(22 cards)
What are the types of epithelial cell surfaces?
The basal surface (facing the basal lamina) and apical surface (facing the free side).
What are tight junctions?
Junctions that seal neighboring cells together in an epithelial sheet to prevent leakage of extracellular molecules between them; helps polarize cells.
What are adherens junctions?
Junctions that join an actin bundle in one cell to a similar bundle in a neighboring cell.
What are desmosomes?
Junctions that join intermediate filaments in one cell to those in a neighbor.
What are gap junctions?
Junctions forming channels that allow small, intracellular, water-soluble molecules, including inorganic ions and metabolites, to pass from cell to cell.
What are hemidesmosomes?
Junctions that anchor intermediate filaments in a cell to the basal lamina.
What are the types of cell junctions?
Anchoring junctions (adherens, desmosomes, hemidesmosomes), occluding junctions (tight), and channel-forming junctions (gap).
What are the functions of tight junctions?
To seal gaps between cells and “fence”, or separate domains within the plasma membrane of each cell.
What is transcytosis vs. recycling?
Transcytosis is when returned receptors travel to a different domain of the plasma membrane, vs. recycling is when it is returned from where it came.
What transmembrane proteins form tight junctions?
Claudins and occludins.
What types of anchoring junctions are there?
Actin cytoskeleton-linked and intermediate filament-linked.
Where are the actin filament attachment sites?
Cell-cell junctions: adherens junctions
Cell-matrix junctions: actin-linked cell-matrix junction
Where are the intermediate filament attachment sites?
Cell-cell junctions: desmosomes
Cell-matrix junctions: hemidesmosomes
What are cadherins vs. integrins?
Cadherins are proteins that mediate cell-cell attachment (homophilic), whereas integrins are proteins that mediate cell-matrix attachment (heterophilic).
What is cadherin function dependent on?
Ca2+ - the ions bind to sites near each hinge and prevent it from flexing. Cadherins are also strong in numbers.
What is indirect and mediated by anchor/linker proteins?
Cadherin linkage. Linker proteins often assemble at the tail of the cadherin.
What do adherens junctions form?
A continuous adhesion belt encircling epithelial cells. Actin bundles are connected via cadherins.
What is the structure of desmosomes?
Similar to adherens junctions, but link to intermediate filaments instead of actin. The cytoplasmic surface of the plasma membrane interacts with a plaque made of accessory anchor proteins. Keratin intermediate filaments attach to cadherins.
What are the structural components of a hemidesmosome?
Hemidesmosomes anchor epithelial cells to basal lamina, linking laminin outside the cell to keratin intermediate filaments inside it. The linkage is mediated by integrin complexed to a plaque of linker proteins.
What are connexons?
Protein assemblies that penetrate an opposed lipid bilayer. Two connexons joins across an intercellular gap to form a continuous aqueous channel connecting two cells.
What do gap junctions create between cells through the channels?
Electrical and metabolic coupling. Ions like cAMP, IP3, and Ca2+ pass through the channels.
