What distinguishes osmosis from diffusion?

• A. Osmosis involves the movement of solutes
• B. Diffusion requires a selectively permeable membrane
• C. Osmosis refers specifically to the movement of water
• D. Diffusion only occurs in gas phase

Answer: (C)

Osmosis is specifically defined as the movement of water molecules across a selectively permeable membrane in response to a concentration gradient. This means that water moves from an area of lower solute concentration to an area of higher solute concentration until equilibrium is reached. This process is critical for maintaining cell turgor and various physiological processes.

In contrast, diffusion refers to the movement of molecules (which can be solutes or gases) from an area of higher concentration to an area of lower concentration, and it does not specifically involve water. Diffusion can occur in various phases, including solid, liquid, and gas, making it a broader term than osmosis. Thus, identifying osmosis as the movement of water specifically clarifies its distinction from diffusion and is the key reason why this answer is correct.