Let's talk about the different kinds of receptors and
effectors that are in our body.
The first most simple kind of receptor-effector combination
is the steroid drug interaction.
So a steroid is a lipophilic kind of molecule.
It will pass through the membrane because it is lipophilic,
and the receptor is somewhere on the inside of the cell.
A transmembrane receptor is one in which that spends the
entire membrane, and the surface has a port
or a receptor site that binds a drug, and the activity
is underneath and causes an effect within the cell.
Tyrosine kinase is a specific kind of receptor-effector
system, where the tyrosine kinase molecule
binds to the drug on the surface, and the JAK portion of that
receptor complex causes a change within the cell.
An ion channel is a very common type of receptor-effector
combination, where a drug might bind to a site on the ion
channel and cause a flow of something in or out of the cell.
And finally, you can have a G-protein coupled receptor.
So a G-protein coupled receptor is where a drug
binds to the receptor on one protein which causes a change
in the G-protein to move over to another molecule
to cause an effect.
So, let's give an example of a G-protein mediated event.
So here's epinephrine, and it causes cyclic AMP synthesis
within the cell. So the first step is that the drug
epinephrine binds to the receptor
and you can see the receptor is a transmembrane protein.
The receptor makes a change at the G-protein.
And what happens is the G-protein itself
dissociate and binds to an effector molecule,
in this case, adenylyl cyclase.
The effector catalyzes a reaction which increases the
concentration of cyclic AMP.
Cyclic AMP is the most common second messenger out there,
and we call cyclic AMP a second messenger
because it is now the second drug or second molecule
that is going out to do something, the first being the drug.
Now, that cyclic AMP causes a biological effect.
So in this particular case, we're talking about
an increase in heart rate, or a dilation of skeletal muscles,
or it could be a breakdown of glycogen to glucose,
depending on what you're talking about.