Sophomores: Diffusion, Osmois, and Active Transport

For all you sophomores who need to learn and remember simple diffusion, facilitated diffusion, osmosis, and active transport:

Simple Diffusion--simply things moving across a membrane. Think of a pool: if you throw a rock in, it breaks the surface and sinks to the bottom. As simple as that.This happens naturally because things want to move from a high concentration to a low concentration, kind of getting away from themselves and trying to spread out evenly.
Facilitated Diffusion--the same thing as simple diffusion except the objects going across the membrane can't do it themselves. The membrane is built so that many things can't go across by themselves. To do this job, there are channel proteins who do just that: they form a channel so that specific things can cross them. Ex. Aquaporins are just channel proteins for water, which sometimes has hard times crossing membranes.
Osmosis--the diffusion of water.
Active Transport--This is the same process as the two diffusions with an exception: things are moving against nature so there needs to be energy put in to move them. Ex. Things moving from low concentration to high concentration is not allowed so to move across the membrane, energy (ATP) needs to be burned, kind of pulling it inside while it's trying to stay outside.

To remember, think Simple Diffusion is very simple, just crossing a membrane, high to low concentration. Facilitated Diffusion just means the things moving are using a "facility" (channel protein) to help them move across. Osmosis: sorry, but I think you just need to know it means water diffusing. Active Transport can be remembered exactly by its name--when you are being active it takes energy and the thing that's going on is "transport" of objects. So, "actively transporting" is diffusion that takes energy to go against the grain.