Alright, the next topic is part of the subcellular housekeeping is the talk about communication.
That's a good thing to talk about, communicating.
And cells have to do it just the way that all the rest of us have to.
So, this is the third in the sequence of basic housekeeping functions
necessary for every cell to maintain being a cell, not even specializing, just being a cell.
Let's do one of the easy ones first.
This would be an important concept. The gap junction.
This is moving very small molecules between cells and it's through pores established between cells.
So, let's look at this.
We have the plasma membrane of cell one and below it,
the plasma membrane of cell two and there's an extracellular space between them.
If the easiest way for one cell to talk to the other is to make a pore,
a set of channels that communicate between them and that's exactly what a gap junction is.
That's what we're gonna show you here now outlined in green.
And gap junctions are dense arrays of these things that look like little flowers
that are composed of individual proteins called connexins
and you take six connexons together and they make a connexon which is a pore.
That pore will line up opposite a pore on the other side and create a gap junction.
Now, they're not open all the time.
They are only open when we want them to be for cells to communicate
and things like calcium and pH will affect whether a connexon is closed or whether it's open
but when it's open, things have about 1.5 kD, kilodaltons will be able to move across.
That's things like calcium and in fact, gap junctions
are the major way the cardiac cells communicate cell to cell, to cell.
They form these gap junctions and when they're open,
calcium will go into from one cell to the next cell and say, "Contract".
And then, to the next cell and say, "You contract."
And the next one after that, "You contract."
So, the nice coordinated contraction of the heart is because of these guys.
Alright, so, that's one way that cells can communicate one to another, through gap junctions.