Summary Unit 2 - Cells Diffusion

Diffusion
The net movement of particles from an area of higher concentration to lower concentration.
This continues until an equilibrium is reached.
Diffusion is a passive process and requires no energy.
As a result of diffusion molecules reach an equilibrium when they are evenly spread out in a
volume of space.
Simple Diffusion:
Simple diffusion only occurs in liquids and gases as they have enough kinetic energy to diffuse.
This is due to particles always having a constant random motion.
When small, non polar molecules diffuse directly through a cell membrane - simple diffusion
occurs.
Concentration Gradient - higher concentration gradient = faster rate of diffusion. The
concentration gradient slows over time and the difference in concentration decreases until
equilibrium is reached.
Thinner Exchange Surface - thinner = shorter distance = faster
Larger Surface Area = faster rate
Small Particles = allows molecules to diffuse faster
Temperature - increase kinetic energy = increase collisions = increased diffusion




Facilitated Diffusion:
Charged ions, polar ions and larger molecules require facilitated diffusion. It uses protein
channels and protein carriers. It is also passive.