∞ generated and posted on 2016.08.25 ∞
Movement across membranes that does not involve an application of energy.
Passive transport includes passive diffusion as well as facilitated diffusion and osmosis. It contrasts with active transport.
Essentially by definition, passive transport involves only movement of substances across lipid bilayers/membranes down their concentration gradients.
The following video provides a nice though longish overview of movement across lipid bilayers except as via active transport:
The following video illustrates movement across lipid bilayers that doesn't involve an output of energy, a brief animation of the process: