Which term describes the movement of a solution through a filter when the membrane is permeable to water?

• A. Filtration
• B. Reabsorption
• C. Osmosis
• D. Diffusion

Answer: (A)

Filtration is the movement of a liquid and its dissolved substances through a filter driven by hydrostatic pressure. When the membrane is permeable to water, water can pass through easily, and the overall flow of the solution through the filter fits this description. This differs from osmosis, where only water moves across a semipermeable membrane in response to an osmotic gradient, and from diffusion, where solutes move down their concentration gradient without a pressure driving force. Reabsorption is a term used for movement from filtrate back into the blood, not the general filtration process.