Cell Biology Flashcards
What is a tight junction?
In a tight junction, a series of integral protein molecules in the plasma membranes of adjacent cells fuse together, forming an impermeable junction that encircles the cell. They help prevent molecules from passing through the extracellular space between adjacent cells. Found in epithelial cells lining the digestive tract.
What are desmosomes?
“binding bodies” Desmosomes are anchoring junctions - mechanical couplings scattered like rivets along the sides of abutting cells that prevent their separation. Adjacent cells are held together by thin linker protein filaments that extend from the plaques (fit together like a zipper). Intermediate filaments extend from the cytoplasmic side of the plaque across the width of the cell to anchor to the plaque on the cell’s opposite side. Reduce chance of tissue tearing (skin, heart muscle).
What is a gap junction?
A communicating junction between adjacent cells that are very close. Cells are connected by hollow cylinders called connexons (composed of transmembrane proteins). Allow ions, simple sugars, and other small molecules to pass between cells. Present in electrically excitable tissues (heart, smooth muscle), helps to synchronize electrical activity and contraction.
