So, that's things coming into the cell.
Let's talk about moving things out of the cell or exocytosis.
Clearly, it's not a one-way streak.
We also need to move things out.
So, what we're shown here on the left-hand side of the line
showing exocytosis is the Golgi complex packaging up a set of proteins
in a membrane that are going to be destined for export to the outside world.
Those are put into vesicles, translocated to the membrane, there,
and then, they are released into the outside space.
What is shown on that panel is a constitutive secretion.
This happens constantly.
So, cells like the liver cells will make albumin constantly,
and package it up and secrete it into the bloodstream.
Similarly, plasma cells, mature B cells,
will constantly package up and secrete their antibodies,
so you can have constitutive secretion.
On the right-hand side of the line here is actually regulated secretion.
So, that occurs only after a signal.
And this is done, for example, in neuronal synapsis,
where neuron is gonna signal to the next neuron.
It's got a packaged collection of material
that it will then release only when the appropriate stimulus comes across.
Same thing happens in the beta islets of the pancreas.
There, you will pre-package insulin and release it after the appropriate signal.
So, it's shown at the bottom, it's that we're packaging up in a golgi apparatus some protein.
It makes a little vesicle, it makes its way to the cell surface,
and then when we signal appropriately,
it's usually through a membrane receptor interaction that causes a calcium influx,
we will get the vesicle to release its contents into the extracellular space,
and that's often running. So, we can have constitutive or regulated exocytosis.
What is this used for? Well, for protein export.
We've talked about this specific example of antibody from B cells,
plasma cells, from albumin, from hepatocytes.
Various peptide hormones, so again, insulin from the beta islet is a good one.
That's regulated. Pancreatic enzymes too.
We only release pancreatic enzymes when there's something to digest.
So, that is a regulated secretion as well.
We can have it as presynaptic vesicles for the exocytosis,
and cytotoxic T cells have pre-packaged molecules, enzymes,
and pore-forming proteins that are going to be directed
to a target once they have interacted with it. So, this is exocytosis.