4.2 Flashcards
What are cell junctions?
are contact points between plasma membranes of tissue cells
What are the five most important types of cell junctions?
tight junctions, adhering junctions, desmosomes, hemidesmosomes, and gap junctions
What is tight junctions?
consist og weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells. Cells of epithelial tissue that lines the stomach, intestines, and urinary bladder have many tight junctions.
What is adhering junctions?
contain plaque (PLAK), a dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton.
What are cadherins?
transmembrane glycoproteins. Each cadherin inserts into the plaque from the opposite side of the plasma membrane, partially crosses the intercellular space (the space between the cells), and connects to cadherins of an adjacent cell.
What are adhesion belts?
In epithelial cells, adhering junctions often form extensive zones called adhesion belts because they encircle the cell similar to the way a belt encircles your waist. Adhering junctions help epithelial surfaces resist separation during various contractile activities, as when food moves through the intestines.
What is desmosomes?
Like adhering junctions, desmosomes contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another. However, unlike adhering junctions, the plaque of desmosomes does not attach to microfilaments.
