Heme Prosthetic Group - Video Tutorials & Practice Problems
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Heme Prosthetic Group
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in this video, we're going to begin our discussion on the heem prosthetic group that both myoglobin and hemoglobin have. Now, before we get into all of the nitty gritty details on the heme prosthetic group, let's first back up and give you guys some context as to why exactly is this him prosthetic groups so important to myoglobin and hemoglobin anyways? And so, in order to be able to understand why this him prosthetic group is so important, we first need to address the fact that amino acids themselves actually lack affinity to oxygen. And so what this means is that if myoglobin and hemoglobin Onley consisted of amino acids and we're just straight simple proteins, then myoglobin and hemoglobin would lack an affinity oxygen, since again, amino acids like an affinity oxygen. But we already know that both myoglobin and hemoglobin is biological roles involve binding to oxygen, and so they need to have an affinity, the oxygen and so myoglobin and hemoglobin. They actually rely and depend directly on the prosthetic group called him in order to bind to oxygen and perform their biological roles. And so unlike amino acids again, which lack an affinity toe oxygen iron, specifically Iran to plus can actually reversible e buying oxygen in just the way that allows myoglobin and hemoglobin to perform their biological roles. And so if Iran is able to reverse Alay Bayan Oxygen, why can't the iron f e two plus all by itself Iran all by itself be a replacement for the biological rolls of myoglobin and hemoglobin? Well, it turns out that we can't just use Iran Adams all by themselves to replace myoglobin and hemoglobin biological roles, because unbound free iron is actually really, really reactive. And it's so reactive that it will actually turn oxygen into free radicals. And that really leads to our first problem. The fact that Iran all by itself, is not going to be a suitable replacement for myoglobin and hemoglobin role. And again, this is because free Iran, essentially Iran all by itself, Iron Adams all by themselves are going to lead to the generation of free radicals which will create radical chain reactions which we know from our previous courses, can actually damage the cell and or potentially even kill the cell. And so Iran Onley again is not going to be a suitable replacement for myoglobin and hemoglobin. So then how about just taking the iron and the rest of the heme prosthetic group and just using these two to replace myoglobin and hemoglobin? Why couldn't we do that? Well, that leads the problem. Number two that the irony in this free him, if you will, which is essentially him. That's not bound to any protein. Uh, this iron eyes going to be still reactive. It's still gonna be reactive. And so this iron two plus is capable of being oxidized in tow. Iron three plus and Iran three plus is a problem because it does not reversible. Buying oxygen like iron two plus does. And so again, taking the iron in the heem all by themselves is not going to be a suitable replacement for myoglobin. And hemoglobin is biological roles. And so this leads directly into the solution to, uh, getting myoglobin and hemoglobin biological roles. And that is the fact that when we combine free Iran, the rest of the team and hemoglobin molecule that the IRA NTEU plus that's found in this protein bound him over here is going to be much, much less reactive. And because it's less reactive, it's not going to create free radicals, and it's not going to be oxidized in tow. Iron three plus. And so that means that it remains in the form Iran to plus when we combine all three of these, and that means that it's capable of reversible, binding oxygen and performing the biological role. And so what we can say is that this indeed is the correct solution to combine these three. And so now that we have a better idea of why this him prosthetic group is so important to hemoglobin and myoglobin. We can continue on to talk Mawr details about the heme prosthetic group structure, so I'll see you guys in our next video.
2
concept
Heme Prosthetic Group
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So now that we know why the Heene prosthetic group is so important to both myoglobin and hemoglobin and this video, we're going to focus on the structure of the Heene prosthetic group, which really does remind me of a UFO shape. And that's because UFOs are very flat and planer and disk shaped, and so is the structure of the team. And so because UFOs and teams they're so flattened plainer in this shape, we could actually look at them from completely different angles and get a completely different visual representation. So here were clearly looking at the top of the UFO, and that's what makes it look like a dish shaped and so broad and why. And so over here we're looking at the heem from a similar angle from the top of the heap, and that's why it looks so broad in this fashion. However again we can look at this UFO and this heem from a different angle and it can look completely different. And our next video, we'll be able to look at the same heem just from a different angle and get a different visual representation, and so you'll be able to see the same thing in your textbooks and in your class power points. So it's important to be able to understand how the khim is flat and this shape just like a UFO Now. It's also important to note that the heem prosthetic group is mostly a non polar structure and so we can see that down below as well, that most of the structure of the heem here is actually consisting of hydrocarbon chains and hydrocarbon chains are non polar, and so there are a few polar groups on this, uh, team group. But again, most of the structure is non polar. And so because most of the team structure is non polar, it's actually going to be mostly surrounded by non polar amino acids when a deep within the hemoglobin and myoglobin proteins. And so it's important to know that this heem prosthetic group, when it attaches to hemoglobin and myoglobin proteins, it really mainly attaches via non co violent interactions. And so really, there are no covalin interactions that allow the team to attach to the hemoglobin and myoglobin proteins. It's mainly non covalin interactions, such as hydrophobic interactions between all of these non polar groups. Now what's also important to note is that right in the center of this heem prosthetic group here, what we have is an iron atom and Iran to plus Adam, which is really known as Ferris iron. And so the fares Iran or Effie to plus it actually complexes with a plainer tetra pira were ring system. And so this is just really a fancy name for what we see in hemoglobin structure down below. So here in the center, what we have is the him and everything else. Uh, that's surrounding three iron. I'm sorry. Here in the center, what we have is the Iran Adam and everything else that's surrounding the iron Adam. It is referred to as this Tetra PIRA will ring system. Now Tetra again just means four. And so basically what this is saying is that these rings that we see right here are pie are called pi role ring. So we have four pi role rings in this ring system and we already know that it is a plainer structure, meaning that it is flat and this shape just like the UFO. And so the name for this Tetra pyro ring system is actually proto poor foreign nine. And so that is the name, uh, that biochemist biochemists gave to this ring system. And so together the fairest iron F two plus and this proto port for a nine system forms the heem prosthetic group. And so it's important to note here that the heem prosthetic group is really referring to both the iron and the proto poor for and ring system together. And so Iran, proto poor for nine, is an alternative way to symbolize the team. And so that might be something good to know for your exams as well, because your professors might just refer to the him as Iran proto poor for nine. And so now that we've covered the basics of the structure of this team on our next video, we'll be able to look at a different visual angle off this heem group. So I'll see you guys in that video
3
concept
Heme Prosthetic Group
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So in our last lesson video, we already mentioned that the heem prosthetic group kind of resembles a UFO like this one right here, because they're both very flat, plainer and dish shaped. And so, just like we can look at a UFO from different angles, we can look at it from the top view. We can also look at it from the side view, just like we're looking at the side of the UFO over here. And because again, the khim is very flattened plane are similar to this UFO. We can also look at the side of the he Emma's well, and so this representation as well as this representation over here are both looking at the side view of the heat. And so notice that we still have our irony, Adam, right in the center and then branching off the iron. What we have is the rest of the heme prosthetic group, and we're not showing all of the atoms here in this representation. But, uh, this is, um, or simplified version. Now, notice over here with this UFO that it is actually abducting this cow right here. And it looks like our little alien dude has popped out of the spaceship and he's saying E t phone heem And that's because of the heem group right here, of course. And so hopefully all of this will help you guys associate the flat, plainer dish shape of the UFO with the flat, plain, erred structure of the team. And so we already know that the Heene prosthetic group is responsible for reversible binding of oxygen molecules. And so what I want you guys to know is that the oxygen atom actually binds to the Iron Adam above the plane of the khim. And so notice down below that are heem prosthetic group is this flat structure right here and then above the plane of the heem notice we have the oxygen gas molecule that's bound non co violently. And so if we were to show that over here on the right, we would have the oxygen atom bound again above the plane of the him so above the UFO. And of course, theocracy gin is able to bind to the iron atom without reacting to form free radicals because it is also bound to this hemoglobin molecule. And so notice that the Iran Adam in the center is bound to the hemoglobin molecule. And so the next point that I want to make is that carbon monoxide is actually an extremely toxic compound. But for many different reasons. However, one of the reasons that carbon monoxide or CEO is so so toxic is because carbon monoxide can actually bind to the heem stronger than oxygen. And because carbon monoxide binds to the him stronger than oxygen, it can actually out compete oxygen for binding to the Iron Adam. And of course, if carbon monoxide is bound to the iron Adam, then that means that oxygen is not capable of binding. And so you could almost think that the carbon monoxide is almost acting like a competitive inhibitor and just blocking the site for oxygen binding. And so, over here we're showing the heem prosthetic group from the side bound to carbon monoxide. And so what? The point that we want to make here is that carbon monoxide, or CEO will actually bind to the khim three, the iron in the him much stronger than the oxygen gas molecule, making the carbon monoxide extremely toxic. And so now that we've covered the visual representation of the prosthetic group, will be able to show even Mawr visual representation of the him and talk more details about it as we continue forward in our course. So I'll see you guys in our next video.
4
concept
Heme Prosthetic Group
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So now that we know a little bit about the structure of the heem prosthetic group in this video, we're going to focus on the interactions of the Iron Adam in the heem prosthetic group. And so, taking a look at our image down below notice, we're looking at a hemoglobin molecule and more specifically, we're zooming in on one of hemoglobin is heem prosthetic groups. And so it's important to know that the iron atom of the protein bound heem can actually form a total of six non Covalin bonds. Four of those six non Covalin bonds are formed with the nitrogen atoms of the proto poor for nine system. And because these four bonds are formed with the proto poor for nine system, they're going to be found in the same exact plane as the Heene Prosthetic Group. And so, taking a look at our image down below noticed that we have the Iron Two plus Adam right in the middle of the heem prosthetic group. And this iron atom is forming four non co violent bonds with the nitrogen atoms of the proto poor for a nine system, and these four bonds are going to be found in the same exact plane as the Heem prosthetic Group. Now one bond. One of these six non Covalin bonds is going to be formed with what's known as a proximal history in residue. And so proximal just means that it's going to be in close proximity with the irony. And so this one bond with the proximal history and residue is going to be found below the plane of the heme prosthetic group, essentially going below the UFO spaceship, if you will. And so notice. Here we have the Iran Adam and going Below the Heem Prosthetic group. We have what's known as the proximal histamine residue, and so we can label this history in here as the proximal history in residue because it's in close proximity to the Iron Adam. And so this final non Covalin bond, we've got a total of five. So far, the final one is going to be a bond with an oxygen atom, and that oxygen atom is going to bind above the plane of the Heene prosthetic group, as we already knew. And so notice over here. What we have is a team prosthetic group that is not bonded to oxygen and So right now this iron Adam on Lee has five total non Covalin bonds, four with the nitrogen atoms and one with the proximal history. However, as soon as oxygen comes into play, we can get the oxygenated form and so notice that it maintains the same exact five non Covalin bonds. But now it has an additional non Covalin bond going up with the oxygen Adam. And so you can see the exact six non Covalin bombs that the iron forms right here in this side of the image. Now which will also notice, is that there is another history. I mean, that is part of the hemoglobin molecule. So remember that this heem prosthetic group is embedded deep within the hemoglobin protein, and so it's surrounded by a lot of hemoglobin protein. And so here we're not showing this particular history, but it is present, and it really only comes into play when the oxygen is bound, which is why we're on Lee showing it over here on the right. And so this particular histamine is forming a non covalin bond with the oxygen atom, not with the Iran Adam. And so for that reason, this history is a bit further away from the Iran Adam, and so it's not going to be proximal. It's actually going to be distal, and that's because it's distant. So distal is for distant. And again, this history is distant, more distant from the Iron Adam and so down below. You can see that we're saying that a distal histamine residue is actually going to be responsible for stabilizing the oxygen atom in the oxygen bound heem. And it does so via a hydrogen bond, which is another non Covalin bond. So this bond right here is a hydrogen bond. And so this hydrogen bond here is so important because what it does is it prevents the conversion of the Iron Two plus Adam, which is right here, which we know can reverse a ble buying oxygen. Very well. Uh, and it prevents the conversion of this iron two plus two, the Iran three plus. And so we know that the Iron Three plus is not going to be able to reverse a ble bind oxygen. So we do not want this iron two plus to be converted into iron three plus. And so the distal history in helps to ensure that this conversion here does not take place. So it's prevented and additionally, what this distal history and also does is it reduces carbon monoxide ability to bind to the heem group. And so that means that this toxic carbon monoxide is going to be less toxic because of the presence of this distal history informing this non covalin interaction with the oxygen atom. And so really, these are the most dominant and the most important interactions that are formed within the him group. And so now that we understand this and our next video will be able to see how these interactions of the iron atom are very similar in myoglobin as well, so I'll see you guys in our next video.
5
Problem
Problem
When O2 binds to a heme group, the two bonds of Fe2+ that are not planar with the heme are occupied by:
A
One O2 molecule and one Ser amino acid atom.
B
One O2 molecule and one His amino acid atom.
C
One O2 molecule and a nitrogen atom of the heme.
D
Two O2 molecules.
6
concept
Heme Prosthetic Group
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1m
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so like hemoglobin, myoglobin team group forms very similar iron interactions and so we can see that down below. We can see that we have the heem prosthetic group right here, which is of course, embedded deep within the myoglobin protein. And if we zoom in on this even further, what we'll see is we've got the hemoglobin protein here, which is very similar to like a alien UFO spaceship. And so in the middle here we have the Iron Two plus Adam, which is going to be forming at six non Covalin interactions. We know that four of those non co violent interactions are going to be in the same plane as the heem prosthetic group. And then it will have one interaction going below with a history in residue on the iron is directly binding to this history in residue Non CO. Violently. And so that was what makes this the proximal histamine residue because it's in close proximity to the Iron Adam. And then, of course, you can see that we've got the oxygen Adam right here, the 02 right here. And of course, what you'll also notice is that we've got another histamine residue that's part of the myoglobin that is binding to the oxygen atom. And it's not binding to the Iran Adam. And so it's further away from the iron atom. So we could say that it is the distal or the distant history in. And so these are going to be very, very similar interactions to what we talked about in our last lesson video. So now that we know that we can move on to our next video.
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Problem
Problem
The distal histidine residue in myoglobin acts to:
A
Prevent oxidation of the heme Fe2+.
B
Lower the relative affinity for CO.
C
Assist in the binding of O2.
D
Prevent release of N2.
E
a & b.
F
a, b & c.
G
All the above are true.
8
concept
Heme Prosthetic Group
Video duration:
4m
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in this video, we're going to talk about how oxygen binding to the heem prosthetic group actually causes hemoglobin is confirmation all changes and so recall from our previous lesson videos, we said that hemoglobin itself is actually an aloe stare IQ protein. And so, of course, what this means is that it has its inactive T state that inefficiently binds toe lie game, and it also has its active are state that efficiently binds toe lie game. And so what's important to note here is that the binding of oxygen gas, specifically to the Heene prosthetic group actually causes a very slight and subtle change in the heem prosthetic groups confirmation. And so, if we take a look down below, it are image notice on the left hand side. Over here, what we have is de oxygenated hemoglobin, and we can tell it's de oxygenated because the oxygen gas molecule is not bound above the plane of the him. And so we've got the Heene group represented right here and then, of course, below. What we have is hemoglobin, proximal histamine residue, and we know that this is the proximal history and residue because it's in close proximity to the Iron Adam and it's bound directly to the iron atom. And so, of course, what we're showing here is oxygen binding to the him prosthetic group. And on the right, what we have is oxygenated hemoglobin. And so what's important to note here is that the de oxygenated hemoglobin over here on the left, the Iran Adam is actually quite large and it's so large that it actually does not fit into the hole that's in the center of the heem group up here. And so what this means is that the plane of the khim, which is right here, uh, is going to be slightly above the iron Adam and the iron atom is gonna be slightly below the plane of the heat because it's so large when it's not bound to any oxygen. And so what's important to note is that upon binding to oxygen gas, the iron atom of the heme prosthetic group actually becomes significantly smaller. And so what this allows is it allows for the iron atom to shift up into the plane of the him and so notice that upon oxygen binding, the iron atom in the center becomes significantly smaller and because it becomes significantly smaller. The iron Adam actually shifts up into the the heem plane upon oxygen binding. And so now you can see that everything is in the same plane, whereas over here we had the iron below the plane. So there is a very subtle in a very slight confirmation. Confirmation will change in the team's structure. And so really, this slight confirmation all change in the team's structure ultimately causes other hemoglobin protein subunits to change confirmations as well. Specifically, it causes them to change confirmation from the inactive T state towards the active our state. And so, of course, we know this is a sign of positive cooperative ity. And so, uh, this is positive cooperative ity because it's promoting the our state and promoting additional binding of oxygen to other hemoglobin subunits and so in our next topic will be able to talk more about this positive cooperative ity. Um, that takes place between him, a globe INS sub units and also I want to take this time to point out that myoglobin because it only has one single sub unit. It does not display any cooperative idiot all its Onley hemoglobin, which is the al hysteric protein that displays this positive cooperative ity. So this year concludes our lesson. And again, the main takeaways. That oxygen binding to the him group causes hemoglobin is confirmation all changes leading to positive cooperative ity between the hemoglobin subunits. And so I'll see you guys in our next video.
9
Problem
Problem
In hemoglobin, the equilibrium transition from T state to R state is triggered by: