UGGGHHH.... Diffusion

Let's just admit it; diffusion is a boring topic, but it's something we all have to learn. And now I guess I'm going to teach you little sophomores more about diffusion. The basic definition of diffusion is the movement of particles from a high concentration to a low concentration. There are 4 basic types of diffusion: simple diffusion, facilitated diffusion, active transport, and osmosis.

Simple diffusion- Is the movement of particles from a high concentration to low concentration across the membrane. This is natural and does not require energy and is therefore "passive". Ex: Think of spraying Febreze in a large room. At the site it is initially sprayed at it will have a rather high concentration and you can smell it; however, the concentration of the particles will naturally spread into the entire room in such a low concentration that you may not be able to smell it any more.

Facilitated diffusion- This is the transport of substances across membrane from high to low concentration. Accept these substances cross the membrane through channel proteins, because they can't cross the membrane themselves. This also does not require energy. Ex: Think of how the channels of water transport people on inter tubes through a lazy river.

Active transport- This is actually the opposite of diffusion, because the substances are moving from a high to low concentration across the membrane. This does not occur naturally and therefore requires energy. Ex: Think of a fan blowing a smell away from you, the fan is the energy.

Osmosis- Simply the diffusion of water.