1. what does it mean to say particles move from high concentration to low ?
2. what are the factors that affect the rate of diffusion and how do they affect the rate?
3. describe the process of facilitated diffusion across a membrane.
4.what is osmosis and how does it relate to diffusion?
5. what is an isotonic solution? hypertonic? hypotonic? how do these concepts relate to diffusion?

1. This simply means particles will move from areas with a lot of the same particle to areas with less of that particle to even out the concentration of the particle across the entire solution.
2. Two examples are factors that affect diffusion are temperature and surface area. Basically, as temperature increases, so does the rate of diffusion, and as surface area decreases, so does the rate of diffusion.
3. Facilitated transport occurs when a molecule is too large or cannot cross the membrane freely through a channel protein. A vesicle, formed by the plasma membrane, will form around the molecule and slowly make its way through the membrane by interacting with the non polar tails of the phospholipid bilayer.
4. Osmosis is the diffusion of water across a membrane. Basically, this means water moving into and out of cells with its concentration gradient.
5. A solution is isotonic relative to a cell if the concentration of a particular particle is equal both in the solution and in the cell. A solution is hypotonic if the concentration inside the cell is less than the concentration of the solution, which will cause the cell to swell as fluid enters the cell. A solution is hypertonic if the concentration inside the cell is greater than the concentration of the solution, which will cause the cell to shrink as particles leave the cell. These concepts dictate whether or not diffusion will occur and, if it does, which direction it will occur in.

Hope this helps! :)