How is osmosis defined in biological terms?

• A. The movement of solute across a membrane
• B. The diffusion of water across a selectively permeable membrane
• C. The active transport of ions
• D. The process of cellular respiration

Answer: (B)

Osmosis in biological terms is specifically defined as the diffusion of water across a selectively permeable membrane. This process occurs when water molecules move from an area of lower solute concentration to an area of higher solute concentration, aiming to equalize solute concentrations on both sides of the membrane. The selectively permeable membrane allows water to pass through while restricting the movement of certain solute molecules, which is vital for maintaining cellular homeostasis and regulating the internal environment of cells.

Understanding osmosis is crucial because it plays a foundational role in various biological processes, including nutrient absorption, waste removal, and the maintenance of cell turgor pressure in plant cells. As water moves through the membrane, it can lead to significant physiological changes within cells, influencing both their shape and function. Therefore, option B accurately captures this essential biological phenomenon.