BPG Regulation of Hemoglobin

in this video, we're going to begin our discussion on B P G regulation of hemoglobin. So be PG is a molecule that actually does affect hemoglobin, oxygen binding activity. And so be PG is really just an abbreviation for the molecule to three bisphosphonates, glycerin it and the by. Here's a prefix that means two, and the Foss vote is referring to phosphate groups, so B P G has to phosphate groups just like what we can see down below in this image. We have a phosphate group over here and another phosphate group over here. And so this is referring to be PGS structure, which I don't expect you guys to be able to memorize. However, I want you to know that the naming has to do with the structure of the molecule. Now. What I also want you guys to realize is that sometimes this prefix by is replaced with dye, which also means to and so sometimes be PG is abbreviated as D p G. Instead. However, both d. P g and B p g r referring to the same exact molecule down below. The only difference is just a little difference here on this prefix die versus by now moving forward in our course, I'm mainly going to be referring to this molecule S b p G because I found that it's more commonly referred to as B p G. Now this molecule B p G as well see moving forward is really going to act as an al hysteric inhibitor, reducing hemoglobin, oxygen affinity in the tissues and allowing hemoglobin to release even mawr oxygen to the tissues when appropriate. And so what this means is that this molecule, B P G. Is really going to have a very similar effect to carbon dioxide and protons on hemoglobin, oxygen binding activity. And so B P G is going to act just like a negative hetero tropic Allah hysteric inhibitor of hemoglobin. Oxygen finding and again hetero is just referring to the fact that B P G is a different molecule than oxygen. The negative is referring to the fact that this is acting as an inhibitor to decrease hemoglobin, oxygen binding and, of course, recall from our previous lesson videos that negative hetero tropical hysteric inhibitors are going to cause the shift the curve to shift towards the right just like carbon dioxide and protons did for human global activity. So again, you can really think of the effect of B. P. G is being very similar to the effect of carbon dioxide and protons. Now this molecule B P G is actually present within all of our re throw sites, which again are are red blood cells. Um however, as we'll see moving forward, B p g is on Lee going to affect hemoglobin when it's in the tissues. And part of the reason for that is because, uh, the binding site to hemoglobin uh, B P G's binding site to hemoglobin. It is Onley available when hemoglobin is in the T state and so recalled that the T State is the 10th state that binds oxygen in efficiently. And so again, be PG. Just like carbon dioxide in protons is going to be stabilizing the T state further because it binds to the T state now. Because that's true, B P G is actually gonna be always binding to de oxygenated hemoglobin. And of course, B P G is not going to be binding to hemoglobin CO. Violently because that would indicate some kind of permanent or long term um, interaction. Instead be PG interacts with de oxygenated hemoglobin via electro static, non co violent interactions again stabilizing hemoglobin T state as we already mentioned. And so if we take a look at our image down below over here on the left hand side, what you'll notice is we have a little equation to help you guys understand B. P. G's effect. And so notice Over here, what we have is oxygenated hemoglobin and in the presence of B p. G. Um, B p g can actually cause, uh, hemoglobin to release its oxygen. And so, really, this is the expression that we can think about that shows how b p G can lead to mawr oxygen being released because again, when B p. G is present, it will, uh, bind to hemoglobin and cause it to release its oxygen. Now, over here, what we have is an oxygen saturation curve where we have fada or why, or the fractional saturation on the Y axis. And then we have the partial pressure of oxygen and units of tours on the X axis, and we've got these three different curves here. We've got this black curve right here that represents, uh, him a glow guns curve when there is absolutely no b p g that's present and notice that it does have a slight sigmoid curve. But it's not nearly a sigmoid allow as these other two curves that we see over here. So this next curve that we see here is basically hemoglobin with some B p g. Not a lot, but some B p g. And notice that the curve is being shifted, uh, to the right. When we add B p g with respect to the black curve right here, uh, this curve that has some B p g is being shifted to the right. And then this last curve that we see here this orange is one is, uh, hemoglobin with even mawr B p G. So what you'll notice is that when we add even more B p g hemoglobin is curve begins to take even mawr of a sigmoid all shape. And really, we can see that B p g is acting as a negative hetero tropic Alice Derek affect er because of this shift to the right that we see with these curves and so in our next video will be able to talk Maura about how b p g Onley effects hemoglobin, oxygen activity when it's in the tissues and not in the lung, So I'll see you guys in that video.

in this video, we're going to focus on the fact that B p g Onley effects hemoglobin, oxygen binding activity in the tissues and not in the lungs. And of course, from our last lesson video. We know that B P G is a negative hetero tropic Alistair IQ inhibitor, which means it's going to decrease hemoglobin oxygen activity. And so B P G is on Lee going to decrease hemoglobin oxygen binding activity in the tissues. And the reason for this is because the conditions in the tissues lead to hemoglobin, mainly being in the T state. And of course, as we know from our previous lesson video, it's the T state that accommodates a binding site for B P G. Now, on the other hand, BBg has a very minimal affect on the oxygen binding in the lung, since hemoglobin is mainly in the our state when it's in the lungs. And of course, the our state does not accommodate a binding site for B P G. And so what's really important to note here is that one B p. G molecule will actually bind per hemoglobin te trimmer, not per hemoglobin sub unit. And so what this means is that one B P G molecule is going to bind to the entire, uh, hemoglobin protein. And there's not going to be one b p. G binding per sub unit. And so, of course, as we already know, be Fiji binding is going to stabilize the T state, uh, in the tissues. And, of course, that's going to cause hemoglobin to release oxygen. So if we take a look at our image over here on the left hand side, But we can say is that there is quite a low concentration of oxygen in the tissues. And so, upon arrival to the tissues, we know that hemoglobin is going to arrive from the lungs fully oxygenated. And so a soon as this oxygenated hemoglobin arrives to the tissues, it's going to encounter the High Co two and the High H Plus that's present in the tissues. And the CO two and H Plus is so high that it's going to bind to the hemoglobin and transition it into the T state, causing Hey Mago been to release its oxygen and, of course, noticed that when hemoglobin is in the T state that it's B p G binding site is available, and so be PG is ableto bind to the T state and further stabilize the T state over here. And so essentially, we have this equilibrium here by Lucia Liaise principle. If this is being shifted to the right through B p g binding, then this is going to decrease. And, uh, if this decreases, then this equilibrium in order to compensate by the shot, these principle is going to shift even further to the right. So essentially be PG Binding leads to this equilibrium shifting even mawr to the right, which leads to even mawr oxygen release. So we associate B P g in the tissues with even mawr oxygen release. Now, on the other hand, over here on the right hand side, what we have are the conditions in the lungs and so, due to very high concentration of oxygen in the lungs ah, high 02 in the lungs due to constant inhalation of oxygen. Hey, McLovin is mainly going to be in the our state when it's in the lungs. And, of course, the our state does not accommodate a site for BBg to bind. So three are state lacks B p G's binding site. And so notice over here. What we have is hemoglobin that is in the our state again due to the high concentration of oxygen. And when hemoglobin is in the our state noticed that B P G's binding site is not available, so it simply cannot bind. And if it can't bind, then hemoglobin is going to remain exactly the same. And it's our state. And when it's an entire state in the presence of such high oxygen in the lungs, it's capable of binding all of that oxygen. And so be PG again has a very minimal effect on oxygen binding in the lungs because it's always in the our state, mainly in the our state. And so this here concludes our introduction to the effect that B. P G has and in our next video will be able to talk more about the physiological regulation of B P G concentration. So I'll see you guys in that video

in this video, we're going to talk about physiological regulation of B P G concentrations. And so what's important to note is that in our ary throw sites or red blood cells, the normal B P G concentrations at sea level are right around five million Mueller. However, this be PG concentration of five million Mueller at sea level can actually be modified to regulate hemoglobin, oxygen binding under different conditions. And so, at very, very high altitudes, such as on top of Mount Everest, there is significantly less oxygen available in the atmosphere for hemoglobin toe bind in comparison to sea level. And so, if we take a look at our oxygen binding curve down below notice on the Y axis, we have the fractional saturation theater, or why and on the X axis. What we have is the partial pressure of oxygen and units of tours. And so notice that we have these three vertical dotted lines going here, here and right over here, and noticed that this one over here on the far right represents the partial pressure of oxygen in the lungs specifically at sea level, which is right around 100 tours. Then you can see that the partial pressure of oxygen in the lungs, except at high altitudes like on top of a mountain, for instance can be significantly less depending on the height. And here we're showing it at 50 tours, which is half of the partial pressure at sea level here. And then, of course, on the far right. What we have is the partial pressure of oxygen in the tissues, which is still right around 20 tours. And so that's exactly what we were mentioning up above that at high altitudes there's less oxygen available in the atmosphere for hemoglobin to bind. And that's exactly what we're showing right here. Less oxygen, less partial pressure of oxygen. And so we, as humans are able to physiologically regulate the concentration of B p g, uh, in our red blood cells. And so, in order to account for this low partial pressure of oxygen at high altitudes, uh, blood be PG concentrations can be increased, uh, to a value of eight million Mueller. So from the normal five million Mueller all the way up to eight million Mueller and what this does is it allows our hemoglobin molecules to maintain very similar oxygen release, um, as they had at sea level. And so if we take a look down below, uh, at our oxygen saturation curve, notice that we have these three different curves. We have this black curve right here that represents hemoglobin, oxygen binding. When there's zero million Mueller B p g. And then we have this blue curve here that represents hemoglobin, oxygen binding under normal conditions, essentially color coded to this blue at sea level for those of you that live at sea level. So this would be right around five million Mueller B p. G. And then, of course, what we have is this red curve right here, which is shifted to the right, uh, in this corresponds with the hemoglobin oxygen binding curve at high altitudes, which is going to be increasing its B P G up to a value of eight million Mueller B p. G. So basically, what you can see is that the higher value of B p G. The higher concentration of B P G will cause hemoglobin is binding curve to shift further to the right And of course, a shift further to the right, uh, correlates with increased oxygen release so releasing even mawr oxygen, and that's going to be helpful when at high altitudes are oxygen are hemoglobin Molecules are not binding very much oxygen. So again, in order to maintain similar oxygen release, they have to be able to release even mawr oxygen. And so what's important to note here is that people that have anemia, which is defined as low red blood cell count they're also going toe have low hemoglobin. And so they need to be able to account for the lowered hemoglobin that they have, um, by increasing their B P G as well. So they have higher B P G in their blood toe help increase oxygen release on accommodate for the fact that they have less hemoglobin molecules. And really, all of this effect here is part of the reason why athletes like to train at high altitudes, because when athletes train at high altitudes, they can acclimated their cells to releasing higher B P g concentrations. And of course, that allows their Selves to acclimate to releasing uh, even mawr oxygen. Uh, when they return to sea level for that race or whatever it is that they are performing in athletically and So this year concludes our lesson on physiological regulation of B P G concentration, and we'll be able to get some practice utilizing these concepts here in our next few videos, so I'll see you guys there.