Gap Junction

A gap junction is a specialised channel that connects adjacent cells to allow direct communication with each other.  Gap junction allows ions, metabolites such as amino acids and water soluble molecules, but not macromolecules like proteins, to pass through the channel due to it's narrow diameter. The molecules that are able to manoeuvre through the channel play a significant role in intracellular communication.  The key feature of a gap junction is that it enables direct cell to cell communication without needing signalling molecules to travel to extracellular space or to other organelles.  Another key feature that sets gap junction from the other cell signalling types, is that a gap junction allows communication to flow in both directions between the adjacent cells.  The main purpose of this bi-directional communication is to normalise the conditions between communicating cells.  In addition, the bi-directional communication can assist in spreading the message between the cells caused by any extracellular signals, therefore the cells are able to ellicit a response and coordinate their actions rapidly.