Welcome to Pharmacology by Lecturio. My name is Dr. PJ Shukle and I'm going to introduce you to the science of Pharmacology
which is the science of drugs. Today we are going to talk about introduction to kinetics which is the way drugs interact with the
human body. One of the things that I want to put forward to you for your board exams and when you are practising for your tests,
is you don't need to know the brand names. I will put them there because they are useful in real practice. But remember that
brand names are going to differ with time. Sometimes some brand names expire and other brand names come into play and they are
also different in different regions in the world. Let's start with a question. So here is a great example of a question that
you are going to see on your board exam. The following dose response curve was isolated from a substance. Choose the number
that defines each substance. So you have a green curve that is 1 and 3. You have a black curve, that's 1 alone. You have a
yellow curve that's 1 and 2. And you have a plum coloured curve that's 1 and 4. So, we are going to define which one
each is. So, one of them is an allosteric activator. One of them is an active drug. One of them is a competitive inhibitor.
And one of them is an allosteric inhibitor. So what do these terms mean? Before we answer the question let's take a look
at how drugs act on a receptor. So you can see the grey ball which is the agonist. It goes into a receptor bay and it fits perfectly.
That is an agonist. That's a drug. A competitive inhibitor will also fit into the same bay, and block the agonist from binding
to that receptor. An allosteric activator, is something that binds to a different place on the same molecule.
So, allo means different, and steric means shape. So it's a different shape, it's a different place
on the molecule, but it activates the activity of the drug. An allosteric inhibitor is something that acts on the different part
of a molecule, but inhibits the action of the drug. So now that we understand what each of those types of molecules
how they are going to react with your receptor, let's try and answer the question. So, A, number 3 is the allosteric
activator. So let's take a look at the green curve. The green curve is 1 and 3. 1 is the active drug, and 3 is the allosteric
activator. So you can see that the curve is much higher. So you get a much greater response when you have an activator that is
allosteric. Let's take a look at C. C, this substance is the competitive inhibitor. Notice how the yellow curve is shifted over
on the graph. That means that you need a higher dose to overcome that competitive inibitor. Now compare that to D which is the
allosteric inhibitor. Notice that the purple or the plum curve actually starts at the same point, but the total response
is much lower and it never gets higher than a certain point and it is always less than 1 alone. So here is a very
important difference between competitive inhibitors and allosteric inhibitors. Guarantee this is going to be a question
on your exam. Guarantee this is going to come up again and again. When we talk about how cells interact with drugs or how drugs
interact with cells, we want to talk about different structural components. So, I'm going to introduce you to the structures
of the cell. Well obviously you know that the membrane is made up of a phospholipid bilayer. We also have glycolipids
and glycoproteins that are on top of the cell and these interact with drugs. So some glycoproteins connect to drugs, some
glycolipids will connect to drugs. We also have integral membrane proteins. These are proteins that cross the entire membrane.
They may or may not be active with a particular drug. You have peripheral membrane protein. This one is on the cellular
cytoplasmic surface of the membrane and it works in a different way. And we are going to point something like that out
to you later. The most important thing I want you to understand about a protein channel right there is that it is transmembrane.
It goes right through the membrane and the core is full of water. So if you have a drug that is dissolvable in water,
it's going to go through a protein channel. Now inside the cells are filaments of cytoskeleton. That's going to be
relevant when we start talking about certain types of drugs later on in our lecture series. There you have it the cell membrane.