Which part of the living system did you change?
Labs / Biology
Osmosis & Tonicity
A single cell floats in a bath of salty water. Move the solute slider and water will cross the semi-permeable membrane on its own, chasing the concentration gradient — swelling the cell, holding it firm, or shrinking it. Add a rigid plant cell wall to see how it changes the ending.
Labs / Biology / Osmosis & Tonicity
Osmosis & Tonicity
A single cell floats in a bath of salty water. Move the solute slider and water will cross the semi-permeable membrane on its own, chasing the concentration gradient — swelling the cell, holding it firm, or shrinking it. Add a rigid plant cell wall to see how it changes the ending.
Why it matters
Why explore this?
Living systems are connected and constantly changing. This model makes one biological process visible so you can test how its parts affect one another.
Explore
Try the model
in 300 mMflux balancedvol 100 %cell at rest
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- Drop the bath to pure water (0 mM). Which way does the water rush, and what happens to an animal cell with no wall?
- Turn the plant cell wall on and go hypotonic again. Why does the cell stop swelling instead of bursting?
- Can you find the bath concentration where the net flux reads "balanced"? How does it compare to the cell's inside concentration?
- Crank the bath up to 600 mM. Why does the inside concentration climb as the cell shrinks, even though no solute crossed the membrane?
- In a hypertonic bath, how does a walled cell's fate differ from a naked one's — plasmolysis versus crenation?
Explain
Make sense of what happened
Explain the process as a chain: a change happens, the system responds, and that response affects what happens next. Use an observation from the model as evidence.
Check
Before you leave
How did the system respond?
How would you explain that response?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.