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11 Cards in this Set
- Front
- Back
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Cell Junctions are important in _______ tissues, and can be observed by _______ microscopy.
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1. epithelial tissue
2. electron microscopy |
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What are the three functional groups of cell junctions?
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1. Occluding Junctions
- tight junctions 2. Anchoring Junctions a) adherens junctions - actin - CC.adhesion belts - CM.local contacts b) IM-filament attachment sites -CC.desmosomes -CM.hemi-desmosomes 3. Communicating Junctions a) gap junctions b) chemical synapses |
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What type of barrier is formed by tight (occluding) junctions? give an example.
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Impermeable barriers!
e.g. Glucose cannot pass through the gut of the lumen. Transporters are required. |
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What is the purpose and the components of Anchoring-Junctions?
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Anchoring Junctions connect the cytoskeleton of a cell to those of its neighbors and/or to the extracellular matrix.
Both Actin and IM-filament types (Cell-Cell or Cell-Matrix) |
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What are Cadherins made of?
What are they activated/regulated by? what type of junction does it form? |
1. Cadherins are made of actin filaments.
2. They are dependent on Calcium for the mediation of a trans-membrane linker glycoprotein 3. They form anchoring junctions |
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What structures are involved in differentiation?
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Actin-filaments in the adhesion belt (cadherins). Contracting elemetns invaginate and bud off.
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What are involved in Focal Adhesions?
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Integrin receptors (alpha and beta subunits) are often involved in focal adhesions. Mediated by fibronectin, laminin, integrins, cadherins
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What are the differences between IM-filament attachment sites, desmosomes and hemidesmosomes?
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Desmosomes are cell-cell attachments and function like rivets
Hemidesmosomes are cell-matrix attachments. Matrix = extracellular matrix, basal lamina, connective tissue IM filaments: Keratin (epithelial) Desmin (heart) Vimentin |
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Gap Junctions (made of connexons) have pores 1.5 nm in size and are responsible for connecting cells in which two ways?
What can fit through these pores? |
Gap Junctions connect cells metabolically and electrically.
Ions, sugars, amino acis, nucleotides, and vitamins can fit through pores. I guess proteins are excluded... |
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What stage of human development are connexons thought to be abundant and why?
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During the embryonic development phase because they allow for the sharing of nutrients and ease of communication.
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Opposite ends of a chemical synapse are kept in proximity by filamentous materials from the basal lamina, define the chemical synapse.
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Chemical Synapse - mechanism where cells communicate indirectly (even though they are not in physical contact).
This space is called the synaptic cleft |
