Question: which of these is best description of passive transport

title: Passive transport
text: Facilitated diffusion , also called carrier - mediated osmosis , is the movement of molecules across the cell membrane via special transport proteins that are embedded within the cellular membrane . Large , insoluble molecules , such as glucose , vesicles and proteins require a carrier molecule to move through the plasma membrane . Therefore , it will bind with its specific carrier proteins , and the complex will then be bonded to a receptor site and moved through the cellular membrane . Facilitated diffusion is a passive process : the solutes move down their concentration gradient and do not require the expenditure of cellular energy for this process . Carrier proteins and channel proteins allow for the diffusion of molecules across the cell membrane . Carrier proteins undergo conformational alterations to allow molecules to pass , while channel proteins form unblocked pores .