In the context of passive transport, does facilitated diffusion require an input of cellular energy (ATP) to move solutes across a membrane?

• A. No; facilitated diffusion occurs only by simple diffusion directly through the lipid bilayer without any proteins.
• B. Yes; facilitated diffusion requires ATP hydrolysis to move solutes through carrier proteins.
• C. No; facilitated diffusion moves solutes down their concentration (or electrochemical) gradient through membrane proteins without ATP.
• D. Yes; facilitated diffusion requires energy because solutes move from low to high concentration.

Answer: (C)