Which term describes the diffusion of water through a selectively permeable membrane?

• A. Osmosis
• B. Framing Square
• C. Open End Wrench
• D. Measuring Tape

Answer: (A)

Osmosis is the diffusion of water across a selectively permeable membrane. The membrane allows water to pass but restricts many dissolved substances, so water moves from the side with higher water potential (lower solute concentration) to the side with lower water potential (higher solute concentration) in an effort to equalize concentrations. This movement continues until an balance is reached. For example, a bag of solution in pure water will gain water and swell, while a bag in a highly concentrated solution will lose water. The other options are tools and have no relevance to how water moves across membranes.