Which term describes diffusion that uses membrane proteins but does not require energy?

Which term describes diffusion that uses membrane proteins but does not require energy?

• A. Facilitated Diffusion
• B. Simple Diffusion
• C. Osmosis
• D. Endocytosis

Answer: (A)

The main idea is diffusion across a membrane that is aided by proteins but does not require energy. When a membrane protein such as a channel or carrier helps a substance move across the membrane down its concentration gradient, that process is facilitated diffusion. It’s passive transport, so no ATP is used, just the natural flow from higher to lower concentration aided by the protein. Simple diffusion, by contrast, doesn’t involve membrane proteins at all and moves solvable molecules directly through the lipid bilayer. Osmosis is water movement and can occur without energy; it is a form of diffusion that may involve water channels (aquaporins), but the term emphasizes water movement rather than protein-assisted transport. Endocytosis requires energy to bud off vesicles, so it’s not diffusion.

The main idea is diffusion across a membrane that is aided by proteins but does not require energy. When a membrane protein such as a channel or carrier helps a substance move across the membrane down its concentration gradient, that process is facilitated diffusion. It’s passive transport, so no ATP is used, just the natural flow from higher to lower concentration aided by the protein. Simple diffusion, by contrast, doesn’t involve membrane proteins at all and moves solvable molecules directly through the lipid bilayer. Osmosis is water movement and can occur without energy; it is a form of diffusion that may involve water channels (aquaporins), but the term emphasizes water movement rather than protein-assisted transport. Endocytosis requires energy to bud off vesicles, so it’s not diffusion.