Facilitated diffusion is a form of passive transport utilizing membrane proteins. When is facilitated diffusion used rather than diffusion? A) Facilitated diffusion is used when energy is required for transport.
B) Facilitated diffusion is used when concentrations must be more closely controlled.
C) Facilitated diffusion is used when molecules need to move more quickly across the cell membrane.
D) Facilitated diffusion is used when molecules cannot diffuse through the cell membrane , because the lipid bilayer repels the polar molecule.