📖 Comprehensive Note
Hypotonic solution — a solution with a lower solute concentration (and therefore a higher water potential) compared to the cell sap or cytoplasm. When a cell is placed in a hypotonic solution, water moves into the cell by osmosis (net movement of water from high water potential → low water potential).
Effects:
- Plant cells: take up water, become turgid; the rigid cell wall prevents bursting (turgor pressure supports plant structure).
- Animal cells (e.g., red blood cells): may swell and burst (haemolysis) because they lack a rigid cell wall.
Osmosis is passive and driven by water potential differences. Hypotonic experiments (e.g., placing cells in distilled water) demonstrate these effects clearly.
🎤 Lyrics + Audio
📊 Line-by-Line Study Guide
| Lyric Line | Explanation |
|---|---|
| When a cell is placed in a hypotonic solution | External solute concentration is lower than inside the cell → water potential outside is higher than inside. |
| Water moves into the cell by osmosis | Osmosis is the net movement of water across a selectively permeable membrane toward the region of higher solute concentration. |
| Cell gains water and swells | Animal cells may swell and burst; plant cells become turgid due to their rigid cell walls. |
| Plant cells become turgid | Turgor pressure from water uptake maintains plant rigidity and is beneficial for support. |
| Animal cells may haemolyse | Red blood cells placed in distilled water undergo haemolysis (bursting) because they lack cell walls. |
💡 Mnemonic
"HYPO = HIPPO (Big)" — HYPOtonic makes cells bigger (they swell). (Think "hypo → hippo = big")
❓ Quiz
1. A hypotonic solution has:
2. What happens to plant cells in hypotonic solutions?
3. Red blood cells in distilled water:
4. What drives osmosis?
5. Why don't plant cells usually burst in hypotonic solution?
🃏 Flashcards
🎯 Drag & Drop
Drag each item into the correct box.
🔬 Demonstrations & Classroom Notes
- Onion epidermis in distilled water: epidermal cells become turgid; plasmolysis reversed.
- Red blood cell in distilled water: visible swelling and haemolysis — good demo for osmosis in animal cells (use appropriate safety and ethical consideration).
- Microscopy tip: use iodine or neutral red to increase contrast when observing plant cells.
📌 Summary
- Hypotonic solution: lower solute concentration outside the cell → water enters by osmosis.
- Plant cells become turgid (beneficial); animal cells may haemolyse (burst).
- Osmosis is passive and driven by water potential differences.