WEBVTT

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So we've thought a little bit about the lungs and the tissue,

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and how there is a kind of (...sing?) relationship between the two,

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where they're trying to send little molecules back and forth,

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so long it try to send, of course oxygen, out to the tissues, right.

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And the tissue is trying to figure out a way to efficiently send back carbondioxide.

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So these are the --the kind of core things are going on, between the two.

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And remember in turns of getting oxygen accross, there're two major ways we said.

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The first one, kind of the easy one, is as dissolved oxygen

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--dissolved oxygen in the blood itself.

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But that's not the major way.

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The major way is when oxygen actually binds hemoglobin --in fact,

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we called it HbO2, and the name of that molecule is oxyhemoglobin.

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So this is kind of how the majority of the oxygen is gonna get delivered to the tissues.

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And on the other side, coming back from the tissue to the lungs,

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you've got dissolved carbondioxide,

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little bit of carbondioxide actually literally comes just right in the plasma.

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But that's not the majority of how carbondioxide gets back.

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The more effective ways of getting carbondioxide back,

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remember we have this protonated hemoglobin.

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And actually --remember when I-- when I said there's a protonated hemoglobin,

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there's gotta be some bicarb floating around in the plasma.

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And the reason that that works is because,

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when they get back to the lungs, the proton --the bicarb,

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actually kind of meet up again, and they form CO2 and water,

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and this happens because there's an enzyme called carbonic-anhydrase,

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inside of the red blood cells.

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So this is where the carbondioxide is actually gets back.

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And of course there's the third way, remember there's also some hemoglobin

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that actually binds directly to carbondioxide in the process,

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you know, it forms a little proton as well,

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and that proton can go to this bussiness, right?

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It can bind to a hemoglobin as well.

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So, there's a little interplay there, but the important ones

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I want to really kind of focus in on, are the fact that hemoglobin can bind to oxygen

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and also in this side, that hemoglobin actually can bind to protons.

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Now the fun part about all this is that there's a little competition, right?

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A little game going on here.

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Because you've got --on the one side you've got hemoglobin binding oxigen,

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and let me draw it twice,

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and let's say this topple an interaction with proton,

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well that proton is gonna wanna snatch away the hemoglobin.

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And so there's a little competition for hemoglobin,

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and here the oxygen kind of gets left out in the cold,

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and the carbondioxide does kind of the same thing we said. We--

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Now we've little hemoglobin bound a carbondioxide and makes a proton in the process,

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but again, that leaves oxygen out in the cold.

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So depending on whether you have a lot of oxygen around,

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if that's the kind of key thing going on,

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or whether you have a lot of these kind of products, the proton or the carbondioxide.

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Depending on which one you have more of, floating around in the --in the tissue, in the cell,

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will determine which way the reaction goes.

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So keeping this concept to mind, then I could actually step back and say, well--

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you know, I think that oxygen is affected by carbondioxide and proton,

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so I could say, well, these two --carbondioxide and protons, are actually --affecting,

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let's say are affecting,

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the --let's say, the affinity,

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the affinity or the willingness of hemoglobin to bind --of hemoglobin-- four oxygen.

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Right, that's one kind of statement you could make by looking at that kind of competition,

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and (the repressing?) come along in that they say, well, I think

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oxygen actually is affecting, you know, depending on which one

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--which perspective you take, you get the oxygen is affecting,

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maybe the affinity of hemoglobin for the carbondioxide and proton.

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--of hemoglobin for CO2 and protons.

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So you could say it from either perspective,

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if I wanna point out is that actually in a sense both of these are true,

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In a lot of times we think, well, maybe it's just saying the same thing twice.

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But actually, these're two separate facts, and they have two separate names.

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So, the first one, talking about carbondioxide and protons,

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their effect is called the {Bohr Effect}.

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See, you might see that word, or this description,

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This is the Bohr Effect.

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And the other one, kind of looking at from the other perspective,

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looking at from oxygen perspective, this should be the {Haldane Effect}.

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That's just the name of it, Haldane Effect.

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So, what is the Bohr Effect and the Haldane effect,

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other than simply saying that the things compete for hemoglobin?

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Well, let me actually bring up a little bit of the (can?) list,

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and let's see if I can diagram this out.

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because sometimes I think a little diagram would really go along when explaining these things.

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So, let's see if I can do that.

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Let's use a little graph and see if you can illustrate the Bohr Effect on this graph.

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This is the partial pressure of oxygen, how much it dissolved in the plasma.

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And this is oxygen content which is to say how much total oxygen is there in the blood,

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and this of course takes an account mostly the amount of oxygen that's bound to hemoglobin.

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So what if I slowly increase the partial pressure of oxygen,

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see how initially not too much is gonna be binding to the hemoglobin,

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but eventually as a few of the molecules bind, you get cooperativity,

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and so then slowly the slopes start to rise, becomes more steep.

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And this is all because of cooperativity,

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oxygen likes to bind where other oxygen have already bound.

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And then it's gonna kind of level off.

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And the leveling off is because hemoglobin is starting to get saturated.

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So there aren't to many extra spots available,

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so you need a lot --a lot of oxygen dissolved in the plasma,

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to be able to seek out and find those extra remaining spots on hemoglobin.

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So let's say we choose two spots.

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One spot, let's say, is high amount of oxygen dissolved in the blood,

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And this, let's say, is a low amount of oxygen dissolved in the blood.

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I'm just kind of choosing them arbitrarily, and don't--

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don't worry about the units.

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And if you are to think of where in the body would be high location,

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that could be something like the lungs, where you have a lot of oxygen dissolved in bloods.

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And low would be, let's say, the thigh muscle where there is a lot of CO2,

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but not so much oxygen dissolved in the blood.

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So these could be two parts of our body, and you--

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you can see that, now if I wanna figure out--

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looking at this curve, how much oxygen is being delivered to the thigh.

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Then that's actually pretty easy, I could just say, well,

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how much oxygen was there in the lungs --or in the blood vessel leaving the lungs--

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And there's this much oxygen in the blood vessels leaving the lungs.

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And there's this much oxygen in the blood vessel leaving the thigh.

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So the difference wherever oxygen is between this two points,

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that's the amount of oxygen that I got delivered.

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So if you want to figure out how much oxygen got delivered to any --any tissue,

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you can simply substract these two values.

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So that's the oxygen delivery.

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But looking at this you can see a kind of interesting point,

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which is that if you want it to increase the oxygen delivery,

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let's say you want it, for some reason, to increase it, become more efficient,

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then really the only way to do that is to have the thigh

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kind of become more hypoxic, as he moves to the left on here,

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that's really becoming hypoxic, or having less oxygen.

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So if he becomes more hypoxic, then yes --you'll, you'll have, you know,

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maybe, a lower point here, maybe a point like this,

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and that would mean a larger oxygen delivery.

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But that's not ideal, you know, when your thighs to become hypoxic,

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you know that --that could start aching and hurting.

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so is there an another way to have a large oxygen delivery

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without having any hypoxic tissue, or tissue that has a low amount of oxygen in it?

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And this is where the Bohr Effect comes into play.

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So, remember that Bohr Effect is that CO2 and proton affect the hemoglobin affinity for oxygen.

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So let's think of a situation --I'll do it in green,

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and in this situation we have a lot of carbondioxide and proton,

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the Bohr Effect thought is, that it's kind of a bit harder for oxygen to bind hemoglobin.

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So if I was to sketch another curve,

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initially, it's gonna be even less impressive, with less oxygen bound to hemoglobin.

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And eventually, once the --once the concentration of oxygen rises enough,

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it will start going up up up, and it does bind hemoglobin eventually,

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so it's not like it'll never bind hemoglobin in the presence of carbondioxide and protons,

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but it takes longer.

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and so the entire curve looks shifted over.

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This-- these conditions of kind of high CO2 and high proton,

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that's not really relevant to the lungs.

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The lungs will think you --for us, you know-- "who cares, we don't really have these conditions".

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But for the thigh, it is relevant.

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Because the thigh has a lot of CO2 and the thigh has a lot of proton.

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Again, remember, high protons means low pH.

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So, you can think it either way.

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So in the thigh, you're gonna get, then, a different point.

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Right, it's gonna be on the green curve, not the blue curve.

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So, we can draw it at the same O2 level, actually being down here.

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So what is the O2 content in the blood that's leaving the thigh?

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Well then, to do it properly out, they'll-- you'll be, actually you'll be over here.

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This is the actual amount. And so O2 delivery is actually much more impressive.

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Look at that. So O2 delivery is inceased because of the Bohr Effect.

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And if you want to know exactly how much it increase,

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I could even show you, I could say, well this amount from here down to here,

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literally the vertical distance between the green and the blue lines,

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so this is the extra oxygen delivered because of the Bohr Effect.

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So this is how the Bohr Effect is so important

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and actually helping us deliver oxygen to our tissues.

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So let's do the same thing now,

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but for the Haldane Effect, and to do this,

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we actually have to switch things around, so our units and our axis are gonna be different.

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So we're gonna have the amount of carbondioxide there,

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and here we'll do carbondioxide content in the blood.

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So let's think through this kind of carefully.

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Let's first start out with increasing the amount of carbondioxide slowly but surely,

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and see that the content goes up.

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and here, as you increase the amount of carbondioxide,

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the content just kind of goes up as the straight line.

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And the reason it doesn't take that S-shape that we had with the oxygen,

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is that there is no cooperativity in binding the hemoglobin.

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It just kind of goes up straight.

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So that's easy enough.

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Now let's take two points like we did before.

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Let's take a point --let's say, up here this'll be high amount of CO2 in the blood,

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and this'll be a low amount of CO2 in the blood.

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So you'd have a low amount, let's say right here, in what part of tissue?

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Well, low CO2, that sounds like the lungs,

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there is not too much CO2 there.

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But high CO2 probably is the thighs, 'cause the thigh is like a little CO2 factories, right?

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So the thigh has a high amount, and the lungs have a low amount.

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So, if I wanna look at the amount of CO2 delivered, we do it the same way with --

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okay, well the thighs had a high amount, this is the amount of CO2 in the blood, remember.

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And this is the amount of CO2 in the blood when it goes to the lungs.

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So, the amount of CO2 that was delivered from the thigh to the lungs,

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is the difference --and so this is how much CO2 delivery were actually getting.

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So just like we had O2 delivery, we have this much CO2 delivery.

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Now, read over the Haldane Effect, and let's see if we can actually sketch out

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another line in the presence of high oxygen, what's gonna happen?

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Well, if there is a lot of oxygen around,

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then it's gonna change the affinity of hemoblobin for carbondioxide and protons.

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So it's gonna low less binding of protons and carbondioxide directly to the hemoglobin.

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And that means that you're gonna have less CO2 content,

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for any given amount of dissolved CO2 in the blood.

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So that line is still a straight line, but it's actually --you notice it's kind of sloped downwards.

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So where is this relevant?

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Where do you have a lot of oxygen?

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Well, it's not really relevant for the thigh,

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because the thighs don't have a lot of oxygen.

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But it is relevant for the lungs.

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It is very relevant there.

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So now you can actually say, "well, let's see what happens"

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Now that you have high O2, how much CO2 delivery are you getting?

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And then-- then you can already kind of see it, it's gonna be more, right?

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because now you got this much, you've got going all the way over here.

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So this is the new amount of CO2 delivery.

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And it's gone up. And in fact, you can even show exactly how much it's gone up by--

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by simply taking this difference. So, this difference right here,

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between the two, this is the Haldane Effect.

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This is the kind of visual way that you can actually see the Haldane Effect.

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So the Bohr Effect and the Haldane Effect, these are two important strategies our body has,

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for increasing the amount of O2 delivery and CO2 delivery

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going back and forth between the lungs and the tissues.

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~o0o~