Exam 4 Flashcards
epithelium
sheets of polarized cells with discrete functional domains at opposite ends
connective tissue
more loosely organized, in which cells are attached to each other, a rigid scaffold, or both
cell-cell junctions
specialized structures where two cells come together
three types of junctions
adhesive junctions
tight junctions
gap junctions
plasmodesmata
special structures in plant cells
adhesive junctions
anchor the cytoskeleton to the cell surface, reply on specialized proteins
types of adhesive junctions
adherens junctions
desmosomes
adherens junctions
cadherin-mediated junctions that interact with actin; are especially prominent in epithelial cells
cadherins are characterized by
repeats in extracellular domain
a transmembrane domain
widely varying cytosolic ends
E-cadherins
has five repeats in extracellular domain, associate in pairs in the plasma membrane, cytosolic portions interact with B-catenin, a-catenin, and actin filaments
E-cadherins are found
epithelial cells
P-cadherins are found
placenta and other tissues
epithelial-mesenchymal transition (EMT)
the breakdown of epithelium into loosely organized mesenchyme cells
desmosomes
button-like points of strong adhesion between adjacent cells in a tissue, abundant in skin, heart muscle, and neck of the uterus
desmosome core
the extracellular space between the two connected cells
desmosomal cadherins
desmocollins and desmogleins
lectins
carbohydrate-binding proteins, promoting cell-cell adhesion by binding specific sugars at the outer cell surface, able to bind to two different cells
cell adhesion molecules (CAMs)
members of immunoglobulin super family, have well-organized loops in their extracellular domains, homophilic interactions occur via these domains
tight junctions
seal epithelial cells leaving no space between the plasma membrane of the adjacent cells
claudins
proteins with four membrane-spanning domains, thought molecules in adjacent cells interlock to form a tight seal
paracellular transport
large extracellular loop forms ion-selective pores and allow passage of specific ions, regulated by claudins
tight junctions block
lateral movement of lipids and proteins in the plasma membrane
lipids are only blocked by the outer monolayer
integral membrane proteins are completely blocked
gap junction
a region where the plasma membranes of cells are aligned and brought into contact, with a very small gap between them, has small pipelines between them, small molecules and ions can pass directly from one cell to another
connexons
hollow cylinders that join adjacent plasma membranes, assembly of six subunits to form a circle