OSMOSIS: water moves, solute cannot
Low solute / more free water → high solute / less free water
No ATP is used.

Dynamic equilibrium

Drag to pan • wheel/pinch to zoom • tap water, solute, membrane or organelle to track

Osmosis: Living Cell Lab

Predict how water balance changes a real cell.

Equal concentrations

Water crosses in both directions at equal rates, so there is no net movement and cell volume stays stable.

Mode

Outside solute300 mOsm

Inside solute300 mOsm

Aquaporins70%

Temperature37 °C

Simulation speed1×

Zoom100%

Focused objectCell membrane

Outside solutionIsotonic

Net water flowBalanced

Cell volume100%

Cell outcomeNormal

Cell-volume historypercent of normal

Teacher / Demo presets

Laser annotation

Core idea

Osmosis is the net movement of water through a selectively permeable membrane. Water moves from the side with lower solute concentration and higher free-water concentration toward the side with higher solute concentration and lower free-water concentration.

Three environments

Hypotonic outside: water enters; an animal cell swells and may lyse.
Isotonic outside: equal movement in both directions; volume stays stable.
Hypertonic outside: water leaves; the cell shrinks or crenates.

Learning objectives

Predict water direction from solute concentration.
Distinguish tonicity from the amount of water present.
Explain dynamic equilibrium in an isotonic solution.
Connect osmosis to cell volume and membrane integrity.
Explain how aquaporins change rate but not direction.

Suggested experiments

Choose hypotonic, then close aquaporins and compare speed.
Set outside solute to maximum and watch crenation.
Use Step to inspect individual water crossings.
Set equal solute values and observe two-way motion with zero net flow.

Questions for exploration

Why can an isotonic cell still have water crossing its membrane? Why do plant cells tolerate hypotonic surroundings better than animal cells?

Score0 / 7