So now that we've introduced myoglobin's hill plot in our last lesson video, in this video we're going to introduce hemoglobin's hill plot. And so unlike myoglobin's protein ligand data which was relatively easy considering that it formed just a single straight line with a slope of 1 on a hill plot. Hemoglobin's protein ligand data on the other hand is much more complicated since it seems to form 3 identifiable lines rather than just a single line when plotted onto a hill plot. And so if we take a look at the hill plot down below in our image over here on the right hand side, notice that it's showing you myoglobin's protein ligand data here with this black line which is again relatively easy considering that it forms just a single straight line with a slope of 1. But notice that we're also showing you hemoglobin's protein ligand data here in red which is clearly much more complex since it does not form a single straight line. And so the complexity of hemoglobin's hill plot has to do with the complexity of hemoglobin structure. And so recall that Hemoglobin is an allosteric protein with multiple subunits that display positive cooperativity. And so, over here what we're saying is that in Hemoglobin's hill plot there are these 3 identifiable lines and so really what we're saying is that hemoglobin's hill plot has 3 identifiable regions. The first region is this region down below here. The second region is this region here in the middle, and the last region is this region up here at the top. And so as we move forward in our course, we're going to break down each of these 3 different regions of hemoglobin's hill plot in separate videos. But for now what I want you guys to know is that these 3 different regions form 3 different identifiable lines and so of these 3 identifiable lines on Hemoglobin's Hill plot, 2 of the hemoglobin lines are actually parallel to myoglobin's line. And so what you'll notice is that this line here highlighted in green if we extend it out, and this line highlighted here in light blue if we extend it out, are both parallel to myoglobin's line here in the middle. And so what we need to realize here is that lines that are parallel are always going to have the same exact slope. And so because myoglobin has a slope of 1, that means that the slope of the lines in these other regions of hemoglobin's hill plot are also going to have a slope of 1 as well. And so of course the slope of the line on the hill plots correspond with the hill constant nh. And so what we're saying is that this green region and this light blue region of hemoglobin's hill plot both have a slope and a hill constant equal to 1. And so what we need to recall is that a slope or a hill constant of 1 means that there's absolutely no cooperativity in those regions. And so, this green region displays no cooperativity and this light blue region displays no cooperativity. Now, that might seem kind of strange since we know from our previous lesson videos that hemoglobin displays positive cooperativity. And so to say that 2 of the 3 identifiable lines display no cooperativity seems kind of weird. But it turns out that the reason this is is because hemoglobin will actually bind to its first and to its last oxygen non cooperatively. And so, as we'll find out moving forward in our course, this light blue region down below corresponds with hemoglobin binding its first oxygen molecule non cooperatively, and this green region up above corresponds with hemoglobin binding its last oxygen non cooperatively. And so really, what allows hemoglobin to display the positive cooperativity that we've been talking about in our previous lesson videos is this 3rd hemoglobin line. And so although 2 of the 3 hemoglobin lines display no cooperativity, this 3rd hemoglobin line has a different and a greater slope than the slope of myoglobin. And so the slope of this yellow region down below in hemoglobin's hill plot, is going to be a slope of 3. And of course, a slope and a hill constant greater than 1, which would include 3, is going to suggest positive cooperativity. And so really, it's this yellow region highlighted in hemoglobin's hill plot that shows the positive cooperativity that we talked about in our previous lesson videos. And so really there's a lot of information to take in here and so that's why moving forward in our course, we're going to break down each of these 3 different regions of hemoglobin's hill plot, 1 by 1. So, we'll start off with the light blue region. Then we'll move into the yellow region and then we'll talk about the green region all by itself. So, I'll see you guys in our next video when we talk about this light blue region. So, I'll see you guys there.