in today's video we're going to start off by looking at what osmosis is then cover exactly what we mean by water concentration and finally we'll see how all of these ideas apply to cells first though let's quickly recap what diffusion is as we saw in a previous video diffusion is just the net movement of particles from an area of higher concentration to an area of lower concentration for example when oxygen or glucose molecules diffuse down their concentration gradient into a cell if you're not confident with diffusion already then i definitely recommend watching the video on that before continuing on with this video now moving on to osmosis osmosis is really just a special case of diffusion and is specifically the diffusion of water molecules the definition you need to know is that osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration the term water concentration can be a bit confusing so let's just break down what it means basically all we mean by water concentration is the amount of water as compared to the other molecules like sugars or salts that are dissolved in that water and we call these dissolving molecules solutes to see what i mean let's take two beakers each with the same amount of water in it and to make it easier to understand we're going to represent the water as these blue particles if we then add one particle of solute to the left beaker and three particles of solute to the right beaker then the beaker on the right will have a higher concentration of solutes than the one on the left because it has more solute molecules and this means that it must also have a lower concentration of water because it has less water molecules per molecule of solute or if you're talking about the left beaker you could say that it has a lower concentration of solutes and a higher concentration of water either way though the key point to understand here is that it's not the volume of water but the proportion of water compared to solutes that determines the concentration so our left beaky here has a higher water concentration the last thing we need to cover is how all of this applies to cells so let's pretend that this is the inside of the cell and this is the outside and between them is the cell's partially permeable membrane inside our cell we have lots of water particles and a fair few solute particles and then outside we have almost pure water with only a couple of solid particles in this case the outside of the cell has the higher water concentration because there aren't many solutes and so the inside of the cell has the lower water concentration this difference in concentration means that water particles will diffuse from the outside of the cell down the concentration gradient into the cell and it's this process of moving from a region of higher water concentration to a region of lower water concentration that we call osmosis hey everyone amadeus here i just wanted to let you know that we also have a learning platform where you can watch all of our videos practice what you've learned with questions and keep track of all of your progress for the sciences and maths it's completely free so if you haven't already you can check it out by clicking on our logo here on the right or if you'd like to do the lesson for this particular video we put the link to that in the description down below we've also arranged all the videos for this subject in a playlist for you here that's all though so hope you enjoy and i'll see you next time thanks