Diffusion

Definition: The net movement of molecules or ions from a region where they are highly concentrated to one where there is a lower concentration until it is evenly distributed (reaches equilibrium).

• Passive movement
• Down a conc. gradient
• Result of diffusion = dynamic equilibrium

Simple:

• Happens through the phospholipid bilayer (membrane)
• Type of molecule transported = Small, non-polar molecules
• Particles are constantly in motion due to the Kinetic Energy they possess
• Random motion

Facilitated:

• Channel and carrier proteins are used (see Fluid Mosaic Model)
• Passive
• Large or polar molecules are transported
• Specificity…