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30 Cards in this Set
- Front
- Back
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where does freeze fracture cut between?
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between plasma membrane?
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what is the P-face of freeze fracture?
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replica of inner leaflet
backed by Protoplasm |
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what is the E-face of freeze fracture?
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replica of outer leaflet
backed by Extracellular Fluid |
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where is the zonula occludens found?
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as part of the junctional complex
most apical |
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what is the zonula occludens made up of?
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sealing strands, which are rows of intramembraneous particles that encircle the cell
they are composed of "occludin" and "claudins" and link to actin filaments |
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what does the zonula occludens look like on freeze fracture?
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it looks like ridges on the P face and grooves in the E face
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where is the zonula adherins found?
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as part of the junctional complex; only in epithelia
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what is the zonula adherins made up of?
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bundle of actin filaments anchored to intracellular attachment proteins
looks like a fuzzy plaque |
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what do the components of the junctional complex look like on EM?
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zonula occludens: fusion of mbns
zonula adherins: 15-20 nm space in between, with fuzzy plaque desmosome: 20-30 nm space, dark attachment plaques on the cytoplasmic sides, with dark intercellular space |
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what is a fascia adherins?
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it is similar to the zonula adherins, but in cardiac muscle
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what are desmosomes?
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spot-like welds holding cells together
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where are desmosomes found?
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in epithelia as part of junctional complex
scattered and in some non-epithelia |
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what are desmosomes made of?
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intermediate filaments anchored into attachment plaques
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what is pemphigus vulgaris?
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autoimmune disease against own desmosomes, causing blisters, fluid loss, and infections
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what is a hemidesmosome?
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anchors basal plasma mbn of epithelial cells to basal lamina of ECM
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what is a hemidesmosome composed of?
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intermediate filaments, w/ integrin transmembrane proteins
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what is bullous pemphigoid?
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disruption of hemidesmosomes, causing separation of the epithelium from the basal lamina
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where are focal contact/ focal adhesion plaques found?
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in fibroblasts, some epithelial cells, smooth muscle
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what are focal adhesion plaques?
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points where stress fibers (bundles of ACTIN filaments and myosin II) anchor into plasma mbn
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what are the transmembrane linker proteins in focal adhesion plaques?
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integrins, which bind to fibronectin in the ECM and bind to intracellular attachement proteins (talin and vinculin) that bind to actin filaments
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what are the transmembrane linker proteins in desmosomes?
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cadherins (e.g. desmogleins, desmocollins)
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what are the transmembrane linker proteins in hemidesmosomes?
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integrins and collagen XVII
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what are the transmembrane linker proteins in zonula adherins?
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cadherins
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what are focal adhesion plaques important in?
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important in cell movement and wound healing
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where are gap junctions found?
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epithelia, smooth and cardiac muscle, nerve, and bone
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what are gap junctions composed of?
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hundreds of paired mbn channels called CONNEXONS, which are bound end to end
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what is a connexon?
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paired mbn channel made up of a hollow tube of 6 connexins
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what are gap junctions used for?
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communicating; cell-signaling and exchange of molecules
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what do gap junctions look like on EM?
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plasma mbns of 2 cells parallel and close (2-4 nm), but not fused
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what do gap junctions like on freeze fracture?
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IMPs of uniform size and crystalline order
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