hello everyone we're back again we're continuing our review of basic cell and physiological Concepts that will help Drive our our thinking throughout the rest of the semester we finished up last time talking about diffusion and facilitated transport the way particular molecules can move across a phospholipid bilayer we're going to take this a step further and actually talk about those Solutions moving and what drives the movement of those solutes or other substances like water so to do so we have to um to bring in a concept that you've all heard about osmosis now again this should not be a New Concept to you we're reviewing this here and it's important for us to review so that we are all starting from the same uh starting point and trying to take this the rest of the semester so let's get started now in this image here we're looking at a bilipid membrane a phospholipid bilipid membrane and the reason that you see that there are kind of of holes in it here or are areas where materials can move from one side to the other is that in most phospholipid bilayer membranes we realize that there probably are cracks in the walls so certain things can get across like water water is one of the few things we realize that can move across a phospholipid bilayer even though it's not supposed to from what we understand of the phospholipid bilayer membrane it does get across in this image the black dots represent water represent water the red dots you see here on your right represent another type of solute sodium chloride now sodium chloride cannot get across a phospholipid bilayer membrane very easily in fact it's almost impossible unless there are channels or carriers allowing it to get across well in that kind of situation if we have a chamber of water that is separated by a phospholipid bilayer like the one we have here and on one side of that membrane there are solutes like sodium chloride that cannot get across water has a tendency to move to that area to where those solutes are that are in higher concentration so here higher concentration of solutes like sodium chloride on one side water has a tendency to move this movement of water is called osmosis osmosis the net diffusion of water across a membrane this net diffusion or this movement is due to solute concentrations the area where there is a higher solute concentration in this case sodium chloride water is moving to that side to that side now this is water has a has a lot of force around it it carries a lot of force with it and so this movement of water is pretty important you can imagine if the sodium chloride that we're looking at is inside a cell and this is the membrane the cell membrane water moving into the cell would cause that cell to swell get bigger because of all the water that is moving into it I got that picture well let's take that a step further this image here kind of a classic image um in in Old physio physiology courses uh like the ones that I was brought up in we actually would demonstrate this concept of Osmosis by using a glass tube that looks just like this one here that's drawn on your slide this one is called an using chamber this boosting chamber literally is a bent glass tube and in the middle of it right in the middle there was an area where you could put a phospholipid bilayer membrane or a membrane of whatever choosing you chose to put there in this case phospholipid bilayer membrane and so as you can see here this is saying a semi-permeable membrane it's possible lipid membrane is a semi-permeable membrane you could fill this chamber with water and remember what we talked just a few minutes ago water seems to be able to get across that bilipid membrane now if there were no solutes here we could pour water on one side it would if it would move over to the other side you would equal that and you'd have equal levels of water on either side of the membrane now in this instance we've added solutes a non-diffusable solute on one side meaning it can't get across the membrane as soon as we added that solute water moves it moves over to try to dilute out those solutes and in doing so you can see how it Rose or caused the level of the water on that left side of the using chamber to rise that movement of water is called Tau you can see the image that I have down below that's how that pressure for water to move that's osmosis that is osmosis and you can see that that pressure associated with the movement of water that osmosis has pushed the level of the water and solutes on the left side of this using chamber much higher than over on the on the right side of the chamber you can look at that here in another drawing or illustration from another text showing you the same sort of thing this here's our situation water here's our semipermeable membrane we've added solutes to one side of the using chamber and you can see how the level rose again well if we modified this situation and we put plunger or some sort of stopper on the right side for this lower image or for the right side of of this uh boosting chamber and we pushed we added some pressure some external pressure well we could level out the levels the air the level of water on both sides of the using chamber but we'd have to be able to exert a fairly large amount of force to push that water back over push that water back over now we can look at it in a slightly different way we could have instead of just having a the using chamber with water we've added into it we have a stopper put on the top of it and then we added the solutes the water or the that stopper would have to exert a certain amount of force to keep water from moving to keep water from moving over kind of like having the stopper or a cap on the top of of you know a a cup that you may have and then adding more and more fluids to it well the cap would try to keep all that fluid inside the amount of pressure that you would need to put on that cap is called osmotic pressure osmotic pressure now we could calculate osmotic pressure by using very classic calculations I am not going to be asking you to do that but I am illustrating it here for you to kind of look at how it would take what it would take for us to be able to actually calculate it out well we're going to have you just understand the concept and understand how much one million or excuse me one osmo lives one one osmotic Force I guess you could say so one osmold is equal to 19 300 millimeters of mercury of pressure that's a huge amount of pressure if you were hit with that amount of pressure it would crush you and literally obliterate you now cells don't have that much pressure why because they're small and the membranes are fairly fragile but we do deal with what are called milliosmoles these millions moles 19.3 millimeters of mercury are something that we will be talking about that are associated with the cell okay a million and that that osmolarity that the Milio's mold is measuring tells us about solute concentrations and the force of water wanting to move so let's take this a step further let's give you a definition to kind of play with here osmolarity is based on the concentration of solute particles whether those particles are able to move across a membrane or not move across a membrane so it's kind of like taking a snapshot of what's what's inside or outside of a cell or what's on one side of a membrane versus the other side of the membrane and to illustrate this a little bit I have this image now in this image trying to let you know this upper Circle here this is representing a normal cell and the volume of a normal cell now when we talk about a normal cell I'm talking about any cell in our human body what we have found is that the osmolarity the concentration of solutes on the inside of that cell is approximately 300 milli osmoles now again I'm not asking you to memorize many numbers this semester um and I've given you reasons for that but this is one number that I do need you to remember that the osmolarity of a normal cell is sitting somewhere around 300 million I'll show you why this is important to us so we have the cell 300 Milli osmoles of solutes on the inside if we were to put that normal cell into a solution let's say a beaker and the fluid in that Beaker had an osmolarity of 300 milliosmoles we put that cell in there that cell would be very happy it would not change the pressure or the amount of solutes outside the cell are the same inside the cell if that makes sense the concentration of solutes inside of the cell are the same as they are outside the cellar 300 Milli osmoles inside 300 million volts outside that's called an isotonic solution and that's the way our cells live in our body inside the cell's 300 million moles outside 300 milliampoles let's say we take that same cell and we put it into a solution that has very few solutes in it let's say pure water pure water that's what you see over here on your right the inside of the cell is 300 Milli osmoles we put it into a solution where it's 200 million moles or less that means there's fewer solutes outside than there are inside the cell if that's the case as soon as that cell gets into that solution water from outside seeing that the inside has more solutes remember osmosis it's going to rush in it's going to cause that cell to swell to swell up because there's more solution wants to dilute out those solutes it makes sense folks make sense you're looting out those Solutions well you better hope the cell is pretty plastic so that it can stretch if not it will burst it will blow open that's why we don't put ourselves in pure water because they would just explode all the water would rush into the cell to dilute out the solutes look at the opposite take a cell 300 million osmoles and we put it into a solution that has a concentration of 400 milliosmoles that means a lot of solutes outside compared to inside the cell well if that were the case that would suck water out of the cell causing it to shrink because the water wants to go to an area where there are higher solutes this could cause the cell to shrink terribly or to literally cause it to lice itself break up because it has no water left it has no water left how does that sound osmolarity osmolarity folks I'm going to take this a step further I have a table here but before we jump into that table I want to bring this up again osmolarity is based on the concentration of solute particles where they're able to cross a cell membrane or not so let's make this human for all of us all right you guys have heard of probably a 0.9 percent saline solution now you probably haven't heard it in that fashion but you have heard it by the name normal saline that's what if you've gone to the hospital because you were dehydrated they would probably give you an IV of normal saline normal saline has a has an osmolarity of 300 Milli osmoles that means it's going to be ISO osmotic with your cells of your body if that makes sense folks now they are not in the hospital going to give you a 0.9 saline solution normal saline with some sugar added to it five percent dextrose one well that would make the solution the solution itself hyper osmotic it has more solutes than inside the cell so what do you think that's going to do that's going to draw water from the cells because there are only 300 million osmoles this would be greater than 300 Milli osmoles all right look below distilled water distilled water and dextrose and dextrose 5 dextrose five percent dextrose here with water that because there's no other solutes there's no sodium chloride or anything else that actually is a hypoosmotic solution hypo osmotic compared to the 300 milliosmoles inside of a cell so if that's the case what's going to happen with water is it going to go into the cell or out of the cell it's going to go into the cell it's going to go into the cell and we can play this game with multiple Solutions with multiple Solutions I need you to remember osmolarity folks osmolarity is based on the concentration of solute particles whether able to cross the cell membrane or not water is always going to move to the area of higher concentration higher solute concentration all right thanks folks we'll see you in our next little video