And these relatively wide channels basically exist between closely packed cells. So let's say this is a cell membrane of one cell, this is a cell membrane of a closely packed adjacent cell, and this is our gap junction. So it basically transverses these two cell membranes. And what it ultimately does is it allows the movement of not only small ions, but also relatively large polar molecules, for instance, sugar molecules. So monosaccharides things like glucose, it allows the movement of amino acids, it allows the movement of nucleotides and so forth. And so there are four important functions of gap junction.