Which transport process uses protein channels and does not require cellular energy?

Which transport process uses protein channels and does not require cellular energy?

• A. Diffusion
• B. Facilitated Diffusion
• C. Osmosis
• D. Active Transport

Answer: (B)

Moving substances across a membrane without using energy relies on down-the-gradient transport that happens through specific membrane proteins. Facilitated diffusion does exactly this: molecules that can’t easily cross the lipid bilayer—often because they’re large or charged—pass through channel or carrier proteins embedded in the membrane. The direction is from higher to lower concentration, so no cellular energy (ATP) is needed. This makes it the best match for a process described as using protein channels without energy input. Osmosis similarly is a passive, energy-free movement, but it’s specifically the diffusion of water through channels called aquaporins, whereas the phrase focuses on solute movement via protein channels, which is the hallmark of facilitated diffusion. Active transport, in contrast, requires energy to move substances against their gradient.

Moving substances across a membrane without using energy relies on down-the-gradient transport that happens through specific membrane proteins. Facilitated diffusion does exactly this: molecules that can’t easily cross the lipid bilayer—often because they’re large or charged—pass through channel or carrier proteins embedded in the membrane. The direction is from higher to lower concentration, so no cellular energy (ATP) is needed. This makes it the best match for a process described as using protein channels without energy input.

Osmosis similarly is a passive, energy-free movement, but it’s specifically the diffusion of water through channels called aquaporins, whereas the phrase focuses on solute movement via protein channels, which is the hallmark of facilitated diffusion. Active transport, in contrast, requires energy to move substances against their gradient.