Which term describes the diffusion of water across a selectively permeable membrane?

Which term describes the diffusion of water across a selectively permeable membrane?

• A. Active transport
• B. Facilitated diffusion
• C. Osmosis
• D. Diffusion

Answer: (C)

Osmosis is diffusion of water across a selectively permeable membrane. Water moves from where there is more water (fewer dissolved particles) to where there is less water (more dissolved particles) until the system reaches balance. The membrane lets water pass but restricts many solutes, so the net movement is driven by differences in solute concentration on the two sides. This differs from general diffusion, which is the spread of any small particles from where they are more concentrated to where they are less concentrated, not specifically water. Facilitated diffusion involves specific solutes moving through membrane proteins and does not describe water movement itself. Active transport requires energy to move substances against their gradient, which is not what happens in osmosis.

Osmosis is diffusion of water across a selectively permeable membrane. Water moves from where there is more water (fewer dissolved particles) to where there is less water (more dissolved particles) until the system reaches balance. The membrane lets water pass but restricts many solutes, so the net movement is driven by differences in solute concentration on the two sides.

This differs from general diffusion, which is the spread of any small particles from where they are more concentrated to where they are less concentrated, not specifically water. Facilitated diffusion involves specific solutes moving through membrane proteins and does not describe water movement itself. Active transport requires energy to move substances against their gradient, which is not what happens in osmosis.