so in the video on hemoglobin's Behavior I told you that hemoglobin behaves in two ways okay where hemoglobin readily binds with oxygen when the partial pressure of oxygen is very high this happens usually in the long alveoli where you're constantly breathing in air which in oxygen and in the body cells where the partial pressure of oxygen is very low hemoglobin readily releases the oxygen to the body cells which makes the oxygen saturation in the red blood cells look so that's quite straightforward now the thing that we have to understand here for this video is there is a bit of an extra thing so one question I'll ask my students is when does hemoglobin readily release oxygen So based on the picture my students will say hemoglobin really releases oxygen when the partial pressure of oxygen is low in reality hemoglobin releases oxygen when a few conditions are met okay uh pH of the blood partial pressure of oxygen and sometimes it also depends on the um temperature okay it also depends on temperature as well so there are a lot of reasons which will cause hemoglobin to readily release oxygen but for the purpose of this we must understand that hemoglobin readily releases oxygen when the partial pressure of oxygen is low and when the partial pressure of carbon dioxide is high functional pressure of carbon dioxide just means the concentration of carbon dioxide in the area okay when those two conditions are met hemoglobin radially releases it okay so what we have to understand is how does the hemoglobin know when to release the oxygen because think about it for the moment right the body cell is especially like a muscle cell or a neuron I use these two cells as examples because these two cells use up oxygen quite quickly a body cell constantly uses up oxygen they constantly use up oxygen due to aerobic respiration okay which will cause them to have a low partial pressure of oxygen that's why they'll always have a low concentration of oxygen within themselves and because they undergo aerobic respiration they constantly produce carbon dioxide which is what causes them to have a high partial pressure of carbon dioxide so the hemoglobin uh so when a red blood cell is passing through these type of cells uh when it's passing through this type of cells and when it's exposed to these body cells the high partial pressure of carbon dioxide causes the oxygen to be readily released from the hemoglobin right and it goes to the body cells so the body cells constantly receive oxygen okay [Music] so this brings a rather important concept and the concept is known as the ball effect now the ball effect is basically a concept or the process that was discovered by a scientist Christian ball and he stated that hemoglobin releases oxygen or hemoglobin releases more oxygen when exposed to an area of higher partial pressure of carbon dioxide example okay let's look at an example here I just want to give you two examples because this is where it becomes very interesting okay let's imagine a body cell okay and the body cell has a low partial pressure of oxygen but it also has a low partial pressure of carbon dioxide this is just an example of a situation okay notice the parameters of the body cells the parameters are low partial pressure of oxygen and low partial pressure of carbon dioxide so when the red blood cell is passing through the body cell will it release the oxygen yes it will release the oxygen but maybe releases only about 80 percent of the oxygen okay so I'm going to plot a graph there percentage oxygen saturation to partial pressure of oxygen so when the partial pressure of oxygen is low for example 2 kilopascals the percentage oxygen saturation becomes 20 let's say the pop the body cell has a partial pressure of oxygen of three kilopascals and the percentage oxygen saturation becomes 40 it releases less oxygen so that's fine and based on the previous video we know that it behaves like a curve so this is good now what I'm gonna do is I'm going to change the condition of the body cell the body cell will still have a low partial pressure of oxygen but the difference now is it has a high partial pressure of carbon dioxide so how would the hemoglobin behave in this case again if the partial pressure of oxygen in the body cell is 2 kilopascals now notice something very interesting the saturation becomes 10 which means to say it releases 90 of oxygen as opposed to 80 earlier so when I put it on the graph that blue color X that I've plotted the graph slightly differently when the partial pressure of carbon dioxide is higher again let's look at it if the body cell has three kilopascals of oxygen and a high partial pressure of carbon dioxide the red blood cell releases or the hemoglobin releases 75 of the oxygen making its percentage oxygen saturation only 25 percent so of course you might be like okay so what if I were to plot a graph okay so you see during the low partial pressure of oxygen okay and low partial pressure of carbon dioxide two kilopascals makes it 20 we kilopasicles makes it 40 okay but in a high partial pressure of carbon dioxide two kilopascals make it 10 percent and three kilopascals makes it 25 percent so if I were to do this and compare the saturation and repeat this experiment over and over again we notice something quite interesting there is a different the curve behaves differently when the partial pressure of carbon dioxide is low and the curve behaves slightly differently when the partial pressure of carbon dioxide is high and what is that difference as the partial pressure of carbon dioxide increases the oxygen dissociation curve shifts to the right and when it shifts to the right it makes hemoglobin more readily release oxygen at areas of low partial pressure of oxygen okay so you might be thinking is this a good or bad thing this is a good thing because if I were to just draw out another curve over here just a side to side comparison okay imagine now the body cell I'm growing two body cells one at the top one at the bottom and I'm also going with blood cells in the capillaries and the red blood cells have a hundred percent oxygen saturation that means they're filled to the maximum capacity of oxygen uh the body cell at the top four kilopascals of oxygen body cell at the bottom four kilopascals of oxygen the only difference is the one at the top has a low partial pressure of carbon dioxide the one at the bottom has a high partial pressure of carbon dioxide so when the red blood cell passes through the body cell at the top look at the curve four kilopascals will correspond to based on the line that I'm highlighting it will correspond to 40 percent so the red blood cell will have a 40 oxygen saturation remaining in it okay so how many percent of oxygen did it release into the body cell it released 60 of oxygen which is good because the body cell needs oxygen right because it has a low partial pressure of oxygen but if you compare to the one at the bottom okay the one at the bottom um the body cell has a low partial pressure of oxygen as well which is which is the same four kilopascals the only difference is it has a high partial pressure of carbon dioxide so in this case you cannot use the Red glove you will have to use the blue graph where I've labeled it as high partial pressure of carbon dioxide so again look at the graph four kilopascals of oxygen so when the mid blood cell reaches the when the red blood cell reaches the body cell what will happen to its oxygen saturation well as you can see if we were to compare it to the graph for kilopascals compared with the blue line okay and we will notice that the percentage oxygen saturation is only 10 so how many percent of oxygen did it release into the body cell it released 90 of oxygen into the body cell so what do we see here it released more compared to the one at the top the one at the top only released 60 of oxygen the one at the bottom released 90 so that's the ball effect the ball effect states that the curve shifts to the right as you can see on the graph okay the red color graph is uh the red color line is on the left the blue color line is on the right due to the higher partial pressure of carbon dioxide and the other thing is it states that hemoglobin readily releases more oxygen in these conditions of course then students will ask the question why well we will look at that in the next part of the video so for our purpose of the lesson to summarize everything all we just have to say here is as follows hemoglobin behaves differently when the partial pressure of carbon dioxide is low and when the partial pressure of carbon dioxide is high in which when the partial pressure of carbon dioxide is high the curve shifts to the right when the curve shifts to the right we call this the ball effect on the ball shift the ball shift is pretty interesting or significant because it states to us that the hemoglobin more readily release oxygen when there is a low partial pressure of oxygen and when there is a higher partial pressure of carbon dioxide it's a bit confusing so I hope you understand this if you're not exactly sure of what I'm explaining here drop me a comment and ask me a question there and I'll try to reply as soon as possible