Osmosis and Water Potential Explained

in this particular video what we are going to be looking at is the other type of passive transport referred to as osmosis so osmosis by definition is just the net movement of water molecules from a region of higher to lower water potential or down the water potential gradient across a partially permeable membrane osmosis is kind of like diffusion but only exclusively for water molecules and osmosis is different from conventional diffusion because osmosis requires something known as a partially permeable or selectively permeable membrane in this case most of the time it's the cell membrane that we are talking about now students will immediately pick on this term known as water potential what is very important to know about what the potential is what a potential is not necessarily the amount of water between two areas it can but it's not exclusively just that so the term water potential it should not be confused with the amount of water because sometimes as you can see here there are two beakers of water one smaller and one larger and they both contain distal water and they can actually have the same water potential so what exactly is the term water potential then water potential just means the tendency of water molecules to move from one area to another the good news is you do not need to memorize this definition but when you say that the water molecule has a higher water potential it has a tendency to move out of that area and if you say that the water molecule has a lower water potential it does not have a tendency to move out of that particular area that means it just wants to stay put in one place so the question here is as follows what affects water potential then water potential is affected by two factors which are solute concentration and the external pressure applied to the solution solutes are just anything that can dissolve in a solvent are being water in this case and solutes can be things like glucose sucrose um ions like sodium ions salts like sodium chloride these are just things that when they dissolve in water they can affect the water potential of the solution what is very important to know is that the higher the solute concentration or the more the solute is present in a solution it will decrease the water potential of the solution and for pressure however the higher the pressure it will actually increase the water potential of the solution so what do I mean by this let's look at it so you see when you talk before we talk about solute concentration and water potential we must always start off with a baseline a baseline is just a place to begin everything my Baseline uh for the purpose of a levels we will choose the easiest baseline or the beginning point and we will start off with a beaker of distilled water and the distilled water is under atmospheric pressure now if you are doing physics you will know that atmospheric pressure is about 76 millimeter mercury you don't need to memorize that and another important thing to also know is distilled water basically means that this particular Beaker contains pure water there are no minerals or any solutes dissolved in it so when you have a beaker of water under atmospheric pressure we will see that the water potential is zero kilo pascals and that's the unit that we use to measure water potential so that is just what I need you to understand so when there is no solutes inside the water in this case distal water and it's only under atmospheric pressure we will say that the water potential is zero kilopascals now the next spot that we actually have to see then is if I have two beakers over here of this the water but instead of just this the water I add some solutes which I have represented in the red colored dots sodium chloride because sodium chloride can dissolve in water one Beaker has less sodium chloride so we will call it a dilute salt solution and the other Beaker contains more sodium chloride so we will refer to it as a concentrated solution remember the higher the concentration of solutes it will cause a decrease in water potential so what we can predict is if distal water has a water potential of zero kilopascal a dilute solution may have a water potential of negative 50 kilopascals and perhaps the concentrated salt solution because it has more salt it will have a water potential of negative 200 kilopascal I don't need you to memorize these values I just need you to understand that distal water is usually represented as a water potential of zero kilopascals and the more solutes you add to the solution the water potential will decrease and become more negative that's a very important point to know so if you were to just compare negative 50 kilopascals and negative 200 kilopascals we will say that negative 50 is less negative and negative 200 is more negative and therefore negative 50 kilopascal has a higher water potential compared to negative 200 kilopascals if you notice over that I'm just throwing five beakers okay and the five beakers have negative 400 kilopascals negative 650 kilopascals zero kilopascal negative 100 kilopascal and negative 300 kilopascals and notice I'm just circling over that water potential that symbol that looks like a trident it is just called the PSI symbol PSI and that is the symbol we use to represent water potential so if you see that symbol do not get very alarmed it's not the pentagram we are not summoning any Devils it is just a symbol to represent water potential now if I were to just write out highest water potential to lowest water potential let's just do a quick activity what I would like you to do is I would like you to arrange the solution from the highest water potential being number one to the lowest water potential being number five so which solution over here has the highest water potential well the first one zero kilopascal is the highest followed by negative 100 negative 300 negative 400 and negative 650 kilopascals that is how you arrange the water Potential from less negative to more negative or highest water potential to lower so what their potential it's just a bit of an extra activity for to make sure that you understand how we measure which water potential is higher and which is lower because sometimes that negative value confuses students right so you just have to be very careful if you see negative 300 and negative 600 negative 300 is less negative negative 600 is more negative that's what that means what we want to see is how does water potential actually work now imagine a let's do a lab experiment and and we have two solutions solution a which is negative 100 kilopascal and solution B which is negative 300 kilopascal and what we have is we have a larger Beaker and the beaker we are going to separate the beaker by a partially permeable membrane to allow osmosis to happen now I will pour the solution a into the left side and our pulse solution B onto the right side remember on the left side is negative 100 kilopascal and on this right side it is negative 300 kilopascals so in this case what will happen is remember osmosis is the movement of water from a higher to lower water potential or from a less negative to more negative water potential so in this case my first question to ask you is as follows which solution on the left or right has a less negative or more negative water potential negative 100 is less negative and negative 300 is more negative which means to say the left side is a higher water potential like side is a lower water potential so there will be a net movement of water for from left to right in this case across a partially permeable membrane what will happen then what will happen then is the solution level on the left will decrease and the solution level on the right will increase because of the influx of water earlier eventually osmosis will stop and when osmosis stops that is said that the solute concentration between the two areas has reached equilibrium where both of them have the same water potential or the same concentration once it has achieved equilibrium there will be no more net movement of water which means to say that water will just move from left to right at a constant and equal rate as I represented in the blue arrow in this case you can say that osmosis has stopped another extra bit that I just want you to know is that pleasure can also affect water potential but in a positive way if I have a beaker of distilled water under atmospheric pressure it is zero kilopascals but if I were to take a plunger and exert some pressure onto the water notice what happens to the water potential it becomes positive 50 kilopascals because I told you that extra pressure can actually increase water potential as well that's just the introduction of Osmosis that we have to know

in this particular video what we are going to be looking at is the other type of passive transport referred to as osmosis so osmosis by definition is just the net movement of water molecules from a region of higher to lower water potential or down the water potential gradient across a partially permeable membrane osmosis is kind of like diffusion but only exclusively for water molecules and osmosis is different from conventional diffusion because osmosis requires something known as a partially permeable or selectively permeable membrane in this case most of the time it&#39;s the cell membrane that we are talking about now students will immediately pick on this term known as water potential what is very important to know about what the potential is what a potential is not necessarily the amount of water between two areas it can but it&#39;s not exclusively just that so the term water potential it should not be confused with the amount of water because sometimes as you can see here there are two beakers of water one smaller and one larger and they both contain distal water and they can actually have the same water potential so what exactly is the term water potential then water potential just means the tendency of water molecules to move from one area to another the good news is you do not need to memorize this definition but when you say that the water molecule has a higher water potential it has a tendency to move out of that area and if you say that the water molecule has a lower water potential it does not have a tendency to move out of that particular area that means it just wants to stay put in one place so the question here is as follows what affects water potential then water potential is affected by two factors which are solute concentration and the external pressure applied to the solution solutes are just anything that can dissolve in a solvent are being water in this case and solutes can be things like glucose sucrose um ions like sodium ions salts like sodium chloride these are just things that when they dissolve in water they can affect the water potential of the solution what is very important to know is that the higher the solute concentration or the more the solute is present in a solution it will decrease the water potential of the solution and for pressure however the higher the pressure it will actually increase the water potential of the solution so what do I mean by this let&#39;s look at it so you see when you talk before we talk about solute concentration and water potential we must always start off with a baseline a baseline is just a place to begin everything my Baseline uh for the purpose of a levels we will choose the easiest baseline or the beginning point and we will start off with a beaker of distilled water and the distilled water is under atmospheric pressure now if you are doing physics you will know that atmospheric pressure is about 76 millimeter mercury you don&#39;t need to memorize that and another important thing to also know is distilled water basically means that this particular Beaker contains pure water there are no minerals or any solutes dissolved in it so when you have a beaker of water under atmospheric pressure we will see that the water potential is zero kilo pascals and that&#39;s the unit that we use to measure water potential so that is just what I need you to understand so when there is no solutes inside the water in this case distal water and it&#39;s only under atmospheric pressure we will say that the water potential is zero kilopascals now the next spot that we actually have to see then is if I have two beakers over here of this the water but instead of just this the water I add some solutes which I have represented in the red colored dots sodium chloride because sodium chloride can dissolve in water one Beaker has less sodium chloride so we will call it a dilute salt solution and the other Beaker contains more sodium chloride so we will refer to it as a concentrated solution remember the higher the concentration of solutes it will cause a decrease in water potential so what we can predict is if distal water has a water potential of zero kilopascal a dilute solution may have a water potential of negative 50 kilopascals and perhaps the concentrated salt solution because it has more salt it will have a water potential of negative 200 kilopascal I don&#39;t need you to memorize these values I just need you to understand that distal water is usually represented as a water potential of zero kilopascals and the more solutes you add to the solution the water potential will decrease and become more negative that&#39;s a very important point to know so if you were to just compare negative 50 kilopascals and negative 200 kilopascals we will say that negative 50 is less negative and negative 200 is more negative and therefore negative 50 kilopascal has a higher water potential compared to negative 200 kilopascals if you notice over that I&#39;m just throwing five beakers okay and the five beakers have negative 400 kilopascals negative 650 kilopascals zero kilopascal negative 100 kilopascal and negative 300 kilopascals and notice I&#39;m just circling over that water potential that symbol that looks like a trident it is just called the PSI symbol PSI and that is the symbol we use to represent water potential so if you see that symbol do not get very alarmed it&#39;s not the pentagram we are not summoning any Devils it is just a symbol to represent water potential now if I were to just write out highest water potential to lowest water potential let&#39;s just do a quick activity what I would like you to do is I would like you to arrange the solution from the highest water potential being number one to the lowest water potential being number five so which solution over here has the highest water potential well the first one zero kilopascal is the highest followed by negative 100 negative 300 negative 400 and negative 650 kilopascals that is how you arrange the water Potential from less negative to more negative or highest water potential to lower so what their potential it&#39;s just a bit of an extra activity for to make sure that you understand how we measure which water potential is higher and which is lower because sometimes that negative value confuses students right so you just have to be very careful if you see negative 300 and negative 600 negative 300 is less negative negative 600 is more negative that&#39;s what that means what we want to see is how does water potential actually work now imagine a let&#39;s do a lab experiment and and we have two solutions solution a which is negative 100 kilopascal and solution B which is negative 300 kilopascal and what we have is we have a larger Beaker and the beaker we are going to separate the beaker by a partially permeable membrane to allow osmosis to happen now I will pour the solution a into the left side and our pulse solution B onto the right side remember on the left side is negative 100 kilopascal and on this right side it is negative 300 kilopascals so in this case what will happen is remember osmosis is the movement of water from a higher to lower water potential or from a less negative to more negative water potential so in this case my first question to ask you is as follows which solution on the left or right has a less negative or more negative water potential negative 100 is less negative and negative 300 is more negative which means to say the left side is a higher water potential like side is a lower water potential so there will be a net movement of water for from left to right in this case across a partially permeable membrane what will happen then what will happen then is the solution level on the left will decrease and the solution level on the right will increase because of the influx of water earlier eventually osmosis will stop and when osmosis stops that is said that the solute concentration between the two areas has reached equilibrium where both of them have the same water potential or the same concentration once it has achieved equilibrium there will be no more net movement of water which means to say that water will just move from left to right at a constant and equal rate as I represented in the blue arrow in this case you can say that osmosis has stopped another extra bit that I just want you to know is that pleasure can also affect water potential but in a positive way if I have a beaker of distilled water under atmospheric pressure it is zero kilopascals but if I were to take a plunger and exert some pressure onto the water notice what happens to the water potential it becomes positive 50 kilopascals because I told you that extra pressure can actually increase water potential as well that&#39;s just the introduction of Osmosis that we have to know

Transcript for:Osmosis and Water Potential Explained

Transcript for:
Osmosis and Water Potential Explained