Which term describes the movement of water through a semi-permeable membrane along a concentration gradient?

Which term describes the movement of water through a semi-permeable membrane along a concentration gradient?

• A. Diffusion
• B. Filtration
• C. Osmosis
• D. Transpiration

Answer: (C)

Osmosis is the movement of water across a selectively permeable membrane from a region of higher water potential (lower solute concentration) to lower water potential (higher solute concentration). The membrane allows water to pass but restricts most solutes, so water shifts to balance solute levels on both sides. This is the best description because it names water as the moving substance and emphasizes the membrane’s selective nature and the driving gradient of solute concentration. Diffusion, while related, is a general spreading of substances from high to low concentration and isn’t limited to water crossing a membrane. Filtration relies on pressure differences rather than solute gradients. Transpiration is the loss of water from plant surfaces due to evaporation, not water movement through a membrane.

Osmosis is the movement of water across a selectively permeable membrane from a region of higher water potential (lower solute concentration) to lower water potential (higher solute concentration). The membrane allows water to pass but restricts most solutes, so water shifts to balance solute levels on both sides.

This is the best description because it names water as the moving substance and emphasizes the membrane’s selective nature and the driving gradient of solute concentration. Diffusion, while related, is a general spreading of substances from high to low concentration and isn’t limited to water crossing a membrane. Filtration relies on pressure differences rather than solute gradients. Transpiration is the loss of water from plant surfaces due to evaporation, not water movement through a membrane.