Osmosis and Diffusion

• Semi-Permeable membrane – allows some things through and keeps other things out (Also called selectively permeable)

Diffusion is the movement of particles across a semi-permeable membrane

Particles move from an area of higher concentration to an area of lower concentration. Generally, smaller

particles move this way, and larger particles cannot get through.

Osmosis is the diffusion of water

Osmosis and Diffusion are both forms of Passive Transport – they

require NO ENERGYBrainPopPassive

In order for larger molecules to move through the membrane, or for particles to move from low to high concentration, energy is needed.

This is called Active Transport.

Which way will the particles move?

Which way will the particles move?

What if they had to move the other way?

What if they had to move the other way?

They would have to move by Active Transport and this would require energy