Which of the following best describes the main difference between diffusion and osmosis?

• A. Diffusion requires energy input from the cell, whereas osmosis does not.
• B. Osmosis occurs only in gases, while diffusion occurs only in liquids.
• C. Diffusion is the movement of any molecules from an area of high concentration to low concentration, while osmosis specifically refers to the movement of water across a selectively permeable membrane.
• D. Osmosis is the movement of solute molecules, while diffusion is the movement of water molecules.

Answer: (C)

Verified step by step guidance

1. Step 1: Begin by understanding the definitions of diffusion and osmosis. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration, driven by the concentration gradient. Osmosis, on the other hand, is a specific type of diffusion that involves the movement of water molecules across a selectively permeable membrane.
2. Step 2: Clarify the key difference between diffusion and osmosis. Diffusion can involve any type of molecule (e.g., gases, solutes) moving down their concentration gradient, while osmosis specifically refers to the movement of water molecules.
3. Step 3: Highlight the role of a selectively permeable membrane in osmosis. Osmosis requires a membrane that allows water to pass through but restricts the movement of solutes, creating a distinction from general diffusion.
4. Step 4: Address the misconceptions in the provided options. For example, diffusion does not require energy input from the cell—it is a passive process. Similarly, osmosis does not occur only in gases; it occurs in liquids and involves water movement.
5. Step 5: Conclude by emphasizing the correct answer: Diffusion is the movement of any molecules from an area of high concentration to low concentration, while osmosis specifically refers to the movement of water across a selectively permeable membrane.