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Now, because the gas constant R is given to us in Joules, so 8.3 114 Joules per kelvin times mole, let's transform these quantities into Joules. | Gibbs Free Energy and Spontaneity.txt |
So this quantity is equivalent to 21,300 Joules and that's a positive value. | Gibbs Free Energy and Spontaneity.txt |
While this quantity, we said just a moment ago we're going to use negative five kilojoules, or equivalently negative 5000 Joules. | Gibbs Free Energy and Spontaneity.txt |
Now, the goal is to ultimately calculate what the Q value has to be, what the ratio of the concentrations of the products to the reactants has to be for the reaction to actually be product favored, for this to be negative 5000 on negative value. | Gibbs Free Energy and Spontaneity.txt |
Now, notice we could have also used negative five joules or negative 1 million joules. | Gibbs Free Energy and Spontaneity.txt |
Basically any negative value here works because any negative value means this reaction will be spontaneous under that Q situation, under that concentration of products and reactants. | Gibbs Free Energy and Spontaneity.txt |
So if we take this equation now and solve for a log of Q, we get that log of Q is equal to so this term is brought to this side. | Gibbs Free Energy and Spontaneity.txt |
So it's this minus this on the top. | Gibbs Free Energy and Spontaneity.txt |
And then we divide by this quantity. | Gibbs Free Energy and Spontaneity.txt |
So 2.33. | Gibbs Free Energy and Spontaneity.txt |
Then the gas constant is 8.3 114 joules per mole times Kelvin. | Gibbs Free Energy and Spontaneity.txt |
And the temperature we're going to assume is, let's say 25 degrees Celsius, so equivalently 298 Kelvins. | Gibbs Free Energy and Spontaneity.txt |
Now, if we solve for Q, we get that Q is equal to ten to the power of this ratio. | Gibbs Free Energy and Spontaneity.txt |
Now this divided by this gives us negative 4.61. | Gibbs Free Energy and Spontaneity.txt |
And so if we carry out this calculation, raised ten to the power of negative 4.61, we get about 2.45 times ten to negative five. | Gibbs Free Energy and Spontaneity.txt |
Now, what this means is when the Q value, when this quantity, when the ratio of the concentration of the product and the reactants is equal to 0.245, the reaction, this reaction here will actually be exergonic, it will be spontaneous and it will be product favored. | Gibbs Free Energy and Spontaneity.txt |
So what we basically show is even though this reaction is undergodonic under standard conditions, when the concentrations of these are equal, if we change the concentrations around, we can actually transform that endergonic non spontaneous reaction into an exergonic spontaneous reaction, as can be seen in the following example where we use the delta g on negative quantity. | Gibbs Free Energy and Spontaneity.txt |
So ultimately it's the delta g that determines whether our reaction under those concentration conditions and that temperature value is actually spontaneous or not. | Gibbs Free Energy and Spontaneity.txt |
This doesn't necessarily have to be negative or positive. | Gibbs Free Energy and Spontaneity.txt |
It doesn't matter what this is. | Gibbs Free Energy and Spontaneity.txt |
It ultimately matters that this is a negative value to actually dictate spontaneity. | Gibbs Free Energy and Spontaneity.txt |
And this concept is important because in our body, our body can change the concentrations and therefore transform these energonic reactions into exergonic spontaneous reactions, as we'll see when we discuss processes such as the crept cycle, glycolysis and so forth. | Gibbs Free Energy and Spontaneity.txt |
Within the developing fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
The organ that is involved in exchanging gas between the mother and the fetus is called the placenta. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, the placenta has other functions as well, but in this lecture we're going to focus primarily on its function in gas exchange. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So let's begin by actually looking at the structure of our placenta. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So this is a diagram of the placement placenta. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So we have the umbilical cord shown here that contains two types of blood vessels. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
We have the umbilical vein shown in red and we have umbilical arteries shown in blue. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So the umbilical arteries carry deoxygenated blood that contains carbon dioxide from the organs and tissues of that fetus and to the placenta itself. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And it carries them to these Corianic villi, these extensions of the Coriane known as the corionic villi. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And within the Corianic villi, we have the tiny blood capillaries that belong to the circulatory system of that fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, these entire Corianic villi are found inside a pool of maternal blood. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And that pool of maternal blood essentially oozes out of these maternal blood vessels that are found in close proximity. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So remember, when the placenta was actually developed, the Corian released these digestive enzymes that digested tiny holes inside these maternal blood vessels. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And those holes essentially allow the blood to actually leak out. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So the way that the exchange takes place is within the maternal blood. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Within the pool of maternal blood we have oxygen. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And oxygen moves down its concentration gradient from the pool of blood and into the capillaries of that fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
At the same time, carbon dioxide is deposited out of the capillaries of that fetus and into the pool of blood and eventually picked up by the maternal blood veins. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And that carries the carbon dioxide to the lungs of that mother and the lungs expel the carbon dioxide to the rest of that environment. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
At the same time, when the lungs inhale, they bring in oxygen. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And that oxygen is ultimately brought into this pooling area of that maternal blood. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, when the oxygen is picked up, it is picked up by these blood vessels. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And then the blood vessels connect to the umbilical vein and umbilical vein. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
This blood vessel, shown in red, actually carries the oxygenated and nutrient filled blood to the organs, tissues and structures found within that developing fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So this is how gas exchange actually takes place. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, the question we want to ask in this lecture is what exactly makes the placenta effective and efficient in actually exchanging that oxygen and what allows it to exchange that oxygen, carbon dioxide, in the right direction. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So remember, we want the placenta not only to exchange the gases quickly and efficiently, but we also want to exchange the gasses in the right direction. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So we must make sure that oxygen always travels into that fetus and carbon dioxide is always removed from that fetus and moves into the blood capillaries and the blood system of the mother. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So there are three factors that affect the efficiency of that placenta, and one of them is the type of hemoglobin molecule that is found inside the blood of that fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So recall that oxygen is actually a nonpolar molecule. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And what that means is it cannot readily dissolve in the blood plasma. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And so it requires a special type of protein carrier to carry it from point A to point B. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And this type of protein is known as hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, the type of hemoglobin molecule found inside adults is different than the type of hemoglobin that is found inside the fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Before we actually see why this is the case, let's discuss what the difference is between the adult and the fetal hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So, in adults, we know that the hemoglobin consists of four subunits. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Two of these subunits are alpha subunits, and the other two subunits are beta subunits. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So we have alpha one and alpha two that combines with beta one and beta two to form a protein tetrimer that we call the dull hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So this is what it looks like. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
We have alpha one, alpha two shown in green, and we have beta one and beta two shown in orange. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, when we form the adult hemoglobin, the adult hemoglobin actually contains a cavity inside a space that is capable of binding a molecule called two three BPG. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, what exactly is two three BPG? | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Well, two three BPG is a molecule that is a byproduct of cellular respiration. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So when cell respiration takes place inside the cells of the adult individual, they produce two three BPG. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And two three BPG can actually bind into that cavity into the space that is found in the adult hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, as soon as the binding takes place, when the two three BPG binds into that space inside the adult hemoglobin, it creates a change in the structure of the adult hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And what that does is it decreases the adult hemoglobin's ability to actually bind to oxygen. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
It lowers its affinity for oxygen. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So when the binding takes place, that adult hemoglobin is much less likely to actually bind oxygen and carry oxygen from point A to point B. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, what about the fetal hemoglobin? | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Well, just like the delt hemoglobin, the fetal hemoglobin also consists of four subunits. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
It contains alpha one and alpha two, as shown in the following diagram. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
But it doesn't contain beta one and beta two. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Instead, it contains a slightly different two subunits gamma one and gamma two. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And when these four subunits create the tetrimer fetal hemoglobin, notice we no longer have that space inside the hemoglobin that can accommodate the two three BPG. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And so, unlike the Dull hemoglobin, the fetal hemoglobin in the presence of two three BPG does not actually bind to two three BPG. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And what that means is if we compare the affinity of these two hemoglobin molecules in the presence of the same concentration of two three BPG, we see that because the fetal hemoglobin doesn't actually bind the two, three BPG, that means its affinity for oxygen will be much higher than the affinity for oxygen of adult hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And if we plot this curve on the x y axis, where the x axis is the partial pressure of oxygen given in millimeters of mercury, and the y axis is the percent saturation of that hemoglobin, we get the following curve. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So the blue curve is the curve that describes the adult hemoglobin, while the red curve describes the fetal hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And notice at the same partial pressure, let's say at 40 degrees partial pressure of oxygen, the adult hemoglobin has much less saturation than the fetal hemoglobin does. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And that's because a fetal hemoglobin does not actually bind to two, three BPG. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And so it is much more likely to actually attract other oxygen molecules and bind to those oxygen molecules. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So we see that the maternal red blood cells have hemoglobin, the adult hemoglobin that binds oxygen much less readily than the fetal red blood cells that contain the fetal hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And as a result, the oxygen will be much more likely to actually move from the blood of that mother and into the blood of that fetus that contains that fetal hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Now, aside from this, there are two other factors that also facilitate the function of the placenta, facilitate the gas exchange process. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So the movement of oxygen from the mother to the fetus can be facilitated by three factors. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So one of them is higher affinity of fetal hemoglobin for oxygen than the adult hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
The other is the fact that inside the blood of the mother, we have a higher concentration of oxygen than inside these capillaries of that fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And so because of this difference in concentration, because the concentration of oxygen is naturally higher inside the blood of that mother than inside the blood of that fetus, oxygen will tend to basically move down its concentration gradient, down its pressure gradient from the mother and to that fetus. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So the final fact that that facilitates the diffusion of oxygen across our placenta is something called the double bore effect. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So let's recall what a bore effect is. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So, the bore effect is basically the ability of carbon dioxide to affect the affinity of hemoglobin. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So the more carbon dioxide we have in the blood, the less likely that hemoglobin will actually bind onto that oxygen. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And conversely, the less CO2 we have in the blood, the more likely our oxygen, our hemoglobin, will actually bind to oxygen. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So what exactly do we mean by double bore effect? | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
Well, let's take a look at the following diagram to see what the double bore effect is. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
So, let's suppose that this purple line is basically our placental membrane. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |
And our gas exchange takes place across the placental membrane, which is basically this coryonic membrane shown right here in purple. | Gas Exchange in Placenta, Fetal Hemoglobin and Double Bohr Effect .txt |