Which of the following best describes the process of diffusion?

• A. The movement of water molecules across a selectively permeable membrane.
• B. The movement of molecules from an area of higher concentration to an area of lower concentration.
• C. The bulk movement of substances into a cell via vesicles.
• D. The active transport of ions against their concentration gradient using ATP.

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of diffusion. Diffusion is a passive transport process where molecules move from an area of higher concentration to an area of lower concentration, driven by the concentration gradient.
2. Step 2: Compare diffusion with other processes mentioned in the options. For example, osmosis specifically refers to the movement of water molecules across a selectively permeable membrane, which is different from diffusion.
3. Step 3: Eliminate options that involve active transport or bulk movement. Active transport requires energy (ATP) to move substances against their concentration gradient, and bulk movement involves vesicles, which are not part of diffusion.
4. Step 4: Focus on the correct description of diffusion, which is the movement of molecules from an area of higher concentration to an area of lower concentration without requiring energy.
5. Step 5: Confirm that diffusion is a passive process and does not involve water molecules specifically (like osmosis) or require ATP (like active transport). This ensures the correct understanding of the term.