Osmosis is defined as what process?

• A. Diffusion of water across a membrane
• B. Movement of solutes across a membrane
• C. Active transport of water
• D. Bulk flow of water and solutes

Answer: (A)

Osmosis is diffusion of water across a selectively permeable membrane. Water moves from where there are fewer dissolved particles (higher water potential) to where there are more dissolved particles (lower water potential), driven by the concentration difference. This movement is passive and does not require energy. The membrane allows water to pass but restricts most solutes, which is why osmosis specifically refers to water diffusion, not diffusion of solutes. It’s not active transport, and bulk flow involves the overall movement of a large volume due to pressure differences, not the selective diffusion of water through a membrane.