Transport & enzymes

Three transports — only one costs ATP.

Compare the three

Diffusion: any particle, high→low, passive.
Osmosis: WATER, partially permeable membrane, passive.
Active transport: against gradient, ATP required, cell chooses direction.

ℹ

Scenario answers

Name the transport + direction + energy source. "Water moved by osmosis from the dilute soil into the concentrated root cell" scores; "water moved in" does not. ℹ

Facilitated diffusion sits between diffusion and active transport

FACILITATED DIFFUSION moves particles down their concentration gradient (like ordinary diffusion, no ATP needed) but uses a specific CARRIER PROTEIN in the membrane to help larger or charged particles cross — something that passive diffusion through the membrane alone could not achieve efficiently. When a resource compares facilitated diffusion with active transport (as in sulphate-ion uptake questions), the key contrast is the DIRECTION relative to the gradient and whether ATP is spent, not just that both involve a protein.

Practice for this standard covers the whole topic — flashcards and quiz.