π§ Osmosis & Turgor Pressure
Place a cell into hypo-, iso-, or hypertonic solution and watch water molecules flow through the semipermeable membrane. Observe turgor pressure, plasmolysis, and lysis in real time. Adjust solute concentration and temperature.
How Osmosis Works
Water moves across a semipermeable membrane from a region of low solute concentration (high water potential Ξ¨) to high solute concentration (low Ξ¨). The driving force is the water-potential difference ΞΞ¨ = βiCRT, where C is solute concentration, R the gas constant, and T absolute temperature. Net flow stops when turgor pressure exactly balances the osmotic gradient β the osmotic equilibrium.
Key Concepts
Hypotonic solution: external
conc. < internal conc. Water enters the cell β the cell swells.
In animal cells this causes lysis; in plant cells the rigid
cell wall builds turgor pressure.
Hypertonic solution:
external conc. > internal conc. Water leaves the cell β the cell
shrinks. Plant cells undergo plasmolysis (membrane detaches
from wall). Animal cells undergo crenation.
Isotonic solution: equal
concentrations β no net flow. Red blood cells are in osmotic
equilibrium with blood plasma at ~280β310 mOsm/L.