TeXes Science Practice Test

Osmosis can best be described as which of the following processes?

1. Active transport of nutrients

2. Diffusion with water

3. Movement of solutes against a concentration gradient

4. The process of filtration

The correct answer is: Diffusion with water

Osmosis is best described as diffusion specifically referring to the movement of water across a semipermeable membrane. In this process, water molecules move from an area of lower solute concentration (where there are more water molecules relative to solutes) to an area of higher solute concentration (where there are fewer water molecules relative to solutes). This movement continues until equilibrium is reached, meaning the concentration of solute is equal on both sides of the membrane. The essential aspect of osmosis is that it does not require energy input, differentiating it from active transport processes. Additionally, while diffusion typically involves the movement of a range of molecules (gases or solutes), osmotic diffusion is specifically related to the behavior of water in relation to solute concentrations. This underscores why the description of osmosis as diffusion with water perfectly captures its fundamental nature in biological systems.