in this video we're going to talk about diffusion and osmosis as well as passive and active transport and facilitated diffusion but let's begin our discussion with diffusion what is diffusion diffusion is the movement of material from a region of high concentration to a region of low concentration so here on the board i have a phospholipid bilayer which makes up cellular membranes now the word bilayer tells us that we have two layers made up of phospholipids molecules such as o2 and co2 carbon dioxide can easily diffuse through this semi-permeable membrane now let's say if we have a large concentration of o2 molecules on the left side and we have a low concentration of o2 molecules on the right side oxygen is going to diffuse from a region of high concentration to a region of low concentration so it's going to move from the left side to the right side that's simple diffusion now this is a form of passive transport the reason why it's called passive transport is because it doesn't require the use of energy let me give you an example so imagine if there's a hill if you place a ball on the top of the hill it's gonna roll down on its own you don't have to put any energy to make it roll down it's just gonna happen naturally so that is a passive system it illustrates the idea of passive transport it's going to move from a high position to a low position on its own without the use of additional energy active transport is the opposite imagine placing the ball at the bottom at the low position the ball on its own will not go up the hill it's just not going to happen that's not a spontaneous process the only way for you to move up the ball to the top is to put energy into the ball you have to push it up there so that is an example of active transport you need to put in energy to move something from a low position to a high position in this picture the red lines represents the phospholipid bilayer here we have an ion channel a carrier protein and this is going to be an aquaporin which allows water to flow into and out of the cell on the top part this is going to be the outside of the cell and at the bottom the inside of the cell first let's focus on co2 co2 is a small nonpolar gas that can easily diffuse across the cellular membrane now in simple diffusion it's going to flow from a region of high concentration to a region of low concentration so it's going to go in this direction so that is an example of diffusion and diffusion is passive transport so anytime you have material moving from a high concentration gradient to a low concentration gradient that is an example of passive transport now let's shift our attention to the sodium ions inside the cell we can see that the concentration of sodium is low and outside the cell sodium has a high concentration so the sodium ions they want to travel into the cell down their concentration gradient however the cell uses atp energy that is adenosine triphosphate to energize this protein pump in sodium ions out of the cell notice that we're using energy to move the sodium ions from a region of low concentration to a region of high concentration that is not diffusion that is an example of active transport so make sure you understand the difference between passive transport and active transport passive transport is the movement of material from a region of high concentration to a region of low concentration and does not require the expenditure of energy whereas active transport is the movement of material from a low concentration to a region of high concentration and it does require the expenditure excuse me the expenditure of energy so it requires the use of atp a good example will be the sodium potassium pump the cell uses atp energy to pump sodium outside of the cell and it takes potassium into the cell now the next situation is glucose and what we have here is a carrier protein notice that the concentration of glucose outside the cell is higher than the concentration of glucose inside the cell so this is going to be an example of passive transport glucose well glucose needs the help of a carrier protein it can't simply diffuse across the semipermeable membrane nevertheless it's going down the concentration gradient it's going from a region of high concentration to a region of low concentration so that is an example of diffusion but because glucose needs the help of a carrier protein to get across the membrane this is going to be called facilitated diffusion it's still diffusion in that we're moving from a high concentration gradient to a low concentration gradient but this diffusion is facilitated by a carrier protein so that's an example of facilitated diffusion so which is another example of passive transport now in the final example the blue circles represent water molecules so the concentration of water outside the cell in this example is high and inside the cell is low water is going to flow through this protein which is known as an aquaporin from a region of high concentration to a region of low concentration so that's another example of diffusion but the diffusion of water has a special name and it's called osmosis so to review passive transport is the movement of material from a region of high concentration to a region of low concentration without the use of energy and it includes examples such as simple diffusion let me change the size of the font here facilitated diffusion as in the case of transporting glucose across the membrane with the use of a carrier protein and osmosis so those are some examples of passive transport and active transport is the movement of material from a region of low concentration to a region of high concentration so we're going up against the gradient and it requires the use of atp energy to make it work so here we're going from high to low down the concentration gradient and here we're going from low to high up the concentration gradient so that's the difference between passive transport and active transport in this picture we have an example of a u-tube the red line represents a semi-permeable membrane and we're going to say that this membrane allows water to pass through but not the solute particles sodium and chloride the solution on the left is a one molar sodium chloride solution i mean on the right on the left we have a 0.3 molar sodium chloride solution so what's going to happen here will water move to the left or to the right the concentration of water on the left side is higher than the concentration of water on the right side the right side is basically a salty solution so it's not pure water it's the concentration of water will be considered low there here the solute concentration is less so the concentration of water is going to be high water is attracted to ions such as sodium and chloride water has partial charges the oxygen part is partially negative and the hydrogen part is partially positive so the hydrogen atoms of water are attracted to the chloride ion and the oxygen atoms of water are attracted to the sodium ion now based on osmosis water is going to move from a region of high concentration to a region of low concentration water is going to be attracted to the high concentration of sodium ions on the right side so what's going to happen is the water level on the right side is going to go up while the water level on the left side is going to go down so let's redraw the picture so after waiting a few minutes the level is going to be different so the water level on the right side is going to be greater than the water level on the left side now the amount of solid particles is still going to be the same now there's two forces that are at play here so there's the driving force of water trying to move to the right to make the solid concentrations equal and also there's the weight of the water that's pushing down against this driving force so you have gravity that's going against this osmotic pressure of water now when these two forces are equal eventually the system will reach a state of equilibrium but that's osmosis it's the movement of water from a region of high water concentration to a region of low water concentration so that's it for this video so now you understand the difference between active and passive transport and you know the difference between diffusion and osmosis so just to review remember diffusion is the movement of any material from a region of high concentration to a region of low concentration whereas osmosis is the diffusion of water is the movement of water from a region of high water concentration to a a region of lower water concentration and so that's it for this video if you like it don't forget to subscribe to this channel and thanks again for watching