Which of the following best describes osmosis?

• A. The active transport of ions using ATP.
• B. The bulk movement of substances into a cell via vesicles.
• C. The movement of solute molecules from a region of low concentration to high concentration.
• D. The diffusion of water molecules across a selectively permeable membrane.

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of osmosis. Osmosis is a type of passive transport, meaning it does not require energy (ATP). It specifically refers to the movement of water molecules.
2. Step 2: Recognize that osmosis occurs across a selectively permeable membrane, which allows certain molecules (like water) to pass through while blocking others.
3. Step 3: Note that osmosis involves the movement of water molecules from a region of higher water concentration (or lower solute concentration) to a region of lower water concentration (or higher solute concentration). This movement aims to balance solute concentrations on both sides of the membrane.
4. Step 4: Compare the given options to the definition of osmosis. Eliminate choices that involve active transport, bulk movement, or solute movement against the concentration gradient, as these do not describe osmosis.
5. Step 5: Identify the correct option: 'The diffusion of water molecules across a selectively permeable membrane,' as it aligns with the definition and characteristics of osmosis.