Tight Junctions, Gap Junctions, and Extracellular Matrix

By Rachel and Sara LembkePeriod 6

TIGHT JUNCTIONS

STRUCTURE Tight junctions are composed of

branching networks of sealing strands. The efficiency of the junction is increased

because each strand acts independently. Sealing strands are formed from a row of

transmembrane proteins embedded in both plasma membranes.

The major types of junction are claudins and occludins.

FUNCTION Hold cells together. Help maintain the polarity of cells. Prevent the passage of molecules

and ions through the space between the cells, which forces the materials to pass through the tissue in order to enter the cell.

GAP JUNCTIONS

STRUCTURE

• A specialized intercellular connection between a multitude of animal cell-types.

• Composed of two connexons which connect across the intercellular space.

• Composed of small channels that permit small molecules to shuttle from one cell to another, linking the interior of adjacent cells.

• Do not seal membranes together, nor do they restrict the passage of material between membranes.

FUNCTION• Directly connects the cytoplasm of two cells which

allows various molecules and ions to pass freely between the cells.

• Allows for direct electrical communication between cells.

• Allows for chemical communication between cells through transmission of small second messengers.

• Prevents large molecules such as nucleic acid and protein from cytoplasmic transfer between cells.

• Ensures that molecules and current passing through the gap junction do not leak into intercellular space.

• Notable use is the electrical synapse found in some neurons.

• Cancer cells generally demonstrate poor or absent gap junction communication.

ANIMAL EXTRACELLULAR MATRIX

STRUCTURE

Includes the intersitial matrix and basement membrane.

A complex network of polysaccharides and proteins secreted by cells.

Is assembled into an organized meshwork in close association with the surface of the cell that produced them.

FUNCTION Provides support and anchorage for

cells Segregates tissues from one another Regulates intercellular

communication Essential for processes like growth,

wound healing, and fibrosis.

Sources

www.wikipedia.org http://www.vivo.colostate.edu/

hbooks/cmb/cells http://www.csm.ornl.gov/SC98/viz/

viz4.html http://www.ncbi.nlm.nih.gov/

bookshelf/br.fcgi?bo Google Images