Which statement best describes the difference between diffusion and osmosis in passive transport across membranes?

• A. Diffusion only applies to gases, whereas osmosis only applies to ions.
• B. Diffusion requires a selectively permeable membrane, whereas osmosis can occur without a membrane.
• C. Diffusion moves substances from low to high concentration using ATP, whereas osmosis moves water from high to low concentration without ATP.
• D. Diffusion is the net movement of any particles down their concentration gradient, whereas osmosis is the net movement of water across a selectively permeable membrane toward the side with higher solute concentration.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of diffusion. Diffusion is the passive movement of particles (such as ions, molecules, or gases) from an area of higher concentration to an area of lower concentration, without the use of energy (ATP). It does not require a membrane but can occur across one if present.
2. Step 2: Understand the concept of osmosis. Osmosis is a specific type of diffusion that involves the movement of water molecules across a selectively permeable membrane. Water moves from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration).
3. Step 3: Compare the two processes. Diffusion can involve any type of particle and does not necessarily require a membrane, while osmosis specifically involves water moving through a selectively permeable membrane.
4. Step 4: Note the direction of movement. Diffusion moves particles down their concentration gradient (high to low concentration), and osmosis moves water toward the side with higher solute concentration, effectively balancing solute concentrations on both sides of the membrane.
5. Step 5: Summarize the key difference. Diffusion is the net movement of any particles down their concentration gradient, whereas osmosis is the net movement of water across a selectively permeable membrane toward the side with higher solute concentration.