Cell Junctions

They link cells together

There are 3 types of cell junctions 1) impermeable junctions (tight junctions) 2) anchoring junctions 3) communicating junctions (gap junctions)

1) conventional transmission electron microscopy 2) freeze fracture microscopy

• take a thin tissue sample • embed onto a hard plastic • cut a thin section of the plastic (50nm) • mount it onto a copper grid • place grid into microscope

• take a thin tissue sample • freeze in liquid nitrogen (196°) • place in the special equipment • bash it to break the tissue sample • put it under a gold filament • run an electric current through it • a layer of gold will build up on the replica • dissolve the tissue

Because it allows us to look at membrane surfaces due to the replica

TJP stop leakage between cells and allow a one way flow of materials between membranes They also allow membrane proteins to stay in the region of the plasma membrane where they are needed

The bladder contains many tight junction proteins whereas parts of the kidney contain few tight junction proteins

They attach the cytoskeleton of one cell to the cytoskeleton of another cell They attach the cytoskeleton of one cell to its surroundings

1) adherens junctions - connect actin 2) desmosomes - connect intermediate filaments

It is an autoimmune disease where the skin cells separate because the body raises antibodies to the desmosomes which keep the cell membranes connected. It will look like huge blisters on the skin.

They were discovered by electrophysiologists

They line up and create aqueous channels between the cytosol of each cell

• coordination of the heartbeat • coordination of smooth muscle contraction • coordination of cilia in the respiratory system