Learn: Osmosis and Water Potential

Welcome!You've already learned about diffusion and active transport in cell membranes, so now let's explore osmosis. This will help you understand how water moves in and out of cells!

What is Osmosis?Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential. It's a passive process, meaning it doesn't require energy.

Water PotentialWater potential measures the ability of water to move. Pure water has the highest water potential (0), and adding solutes lowers water potential. Water moves towards areas with lower (more negative) water potential.

Partially Permeable MembranesA partially permeable membrane allows some substances (like water) to pass through, but blocks others (like large molecules). This is key for osmosis to occur.

Osmosis in CellsIn cells, osmosis affects the movement of water between the cell and its environment. For example, water moves into a cell in a hypotonic solution (higher water potential outside) and out of a cell in a hypertonic solution (lower water potential outside).

Effects of OsmosisOsmosis can cause cells to shrink (plasmolysis in plant cells) or swell (lysis in animal cells). In plants, turgid cells help maintain rigidity, while flaccid cells cause wilting.

Core Practical: Investigating OsmosisIn one practical, you can study osmosis using potato cylinders in solutions of different concentrations. You measure their mass before and after to calculate water movement. This shows how water potential affects osmosis.

Review Time!Great work! You've learned about osmosis, water potential, and their effects on cells. Let's test your understanding with a few final questions.