This sigmoidal graph of oxygen saturation has a bunch of different names, and they're all correct. So use whichever one you like. It can be called the oxygen dissociation curve, sometimes it's the oxygen hemoglobin equilibrium curve, or sometimes people call it the oxyhemoglobin saturation curve. These are not the best names, you know. But I get the job done and either way it's just a sigmoidal curve that is just trying to illustrate the oxygen saturation of hemoglobin at different partial pressures of oxygen. So here on the y-axis, we have our saturation of oxygen, and on the x-axis, we have our partial pressures of oxygen. So what you hopefully will notice is that as the partial pressure of oxygen increases, oxygen saturation increases. Hopefully, you also notice that this is not a straight line, meaning that the rate of oxygen saturation in hemoglobin does not correspond linearly to the partial pressure of oxygen. That's why we say that this has a sigmoidal shape, right? It has that curve to it, and the reason for that is because of the cooperative binding. Right? When oxyhemoglobin only has a little bit of oxygen bound, it's going to take a little bit for it to bind some oxygen, but once it has some oxygen bound that's why the rate of saturation kind of shoots up in this middle region. Right? That's the important thing to take note of is that the rate here at low partial pressure and really high partial pressure is less than in the middle because, essentially that is, as one oxygen is bound here, it's going to make it really easy to bind those next oxygens and then, as one oxygen is released here it's going to make it really easy to release those other oxygens here. So that cooperative binding is what gives the sigmoidal shape of this graph. So with all that, let's make it even more confusing, that curve can actually move to the right and to the left. Now, we're only going to really talk about the right shift, but the left shift is basically just going to be due to the opposite reasons of a right shift. So that right shift we call the Bohr shift. Sometimes it's the Bohr effect, named after the guy who theorized it. And it's essentially a shift of the curve to the right, so, you know, that direction. And, it's going to be due to several factors, we're only gonna look at 2 really. And those two factors are decreasing pH, so, lower pH, things getting more acidic, and also increasing the partial pressure of CO2. So hemoglobin can also bind CO2. However, all you really need to worry about is the fact that increasing partial pressure of CO2 will lower hemoglobin's affinity for oxygen. So more, higher CO2 concentration makes hemoglobin have a lower affinity for oxygen, which is going to, cause it to unload oxygen. Right? Which makes sense because tissues that are consuming a lot of oxygen are going to generate a lot of CO2, which is going to cause an increase in the partial pressure of CO2. So, essentially, the idea there is that tissues that are, performing a lot of cellular respiration, they're consuming lots of oxygen, are going to have a higher, a higher partial pressure of CO2, and this is going to cause hemoglobin to unload its oxygen more efficiently. And we can visualize that on our graph by, having our curve, you know, shift over to the right. So here's my new curve. Sorry. It's so ugly. I'm not an artist. But, essentially, the idea is that now hemoglobin has a lower affinity for oxygen. Right? Because at it will take higher partial pressures to achieve the same level of saturation. That's essentially all that boils down to. And it's just a mechanism that makes hemoglobin more efficient at unloading oxygen in tissues that really need it. Now, the other thing we're gonna look at, as I said, was pH, how pH affects it. So, lowering pH, which could also be thought of as increasing the acid concentration. So lowering pH or increasing acid, however you want to think about it, will result in lowering hemoglobin's affinity for oxygen. Now, the way I like to think about this is that CO2, when it gets into the blood, is going to combine with water and form carbonic acid. Acid means lower pH, so, basically, the more CO2, the more carbonic acid, which means the lower the pH, and that lower pH is going to cause a right shift in the curve. And remember that a right shift in the curve is going to, allow hemoglobin to unload its oxygen more easily. So this is just another way of sort of detecting those CO2 concentrations. Right? Not only is it affected by the partial pressure of CO2, but it's also affected by pH. And that pH fluctuation is going to be in large part due to carbonic acid which comes from CO2. So these are just ways of making hemoglobin better at doing its job, basically. And, you know, as I said, there