Diffusion vs Active Transport
Fundamentally, diffusion is random movement of molecules.
During diffusion, there is a net movement of a substance down its electrochemical gradient.
Lipid bilayer: Lipid soluble substances
Pores or channels: Water and water-soluble substances
Driven by electrochemical gradient. No extra energy is required from external sources.
Molecules are actively transported against electrochemical gradient.
Occurs through transport proteins.
Requires energy from external sources e.g. ATPs.