Osmosis Lecture Notes

Introduction to Osmosis

• Osmosis is the movement of water, a type of diffusion.
• Occurs through a semi-permeable membrane, like a cell membrane.
• Membranes allow water molecules to pass but not larger molecules like salt without assistance.

Characteristics of Osmosis

• Passive Transport: Does not require energy.
• Water moves from high concentration to low concentration areas.
• Water tends to move to areas with high solute concentration (low water concentration).

Understanding Solute Concentration

• Solutes: Substances like salt or sugar dissolved in a solvent (water).
• High solute concentration means low water concentration.
• Water moves towards higher solute concentration to balance concentrations.

Example: Osmosis in a Box

• Imagine a box with a semipermeable membrane.
• Side A: Pure water; Side B: Water with salt.
• Water moves from Side A to Side B as B has higher solute concentration.
• Equilibrium is reached when net water movement is zero.

Osmosis Vocabulary

• Hypertonic: High solute concentration compared to another.
• Hypotonic: Low solute concentration compared to another.
• Isotonic: Equal solute concentration.

Real-Life Examples of Osmosis

1. IV Fluids in Hospitals:

   • Pure water IVs are dangerous; blood cells have higher solute concentration.
   • Cells would swell and burst if pure water were used.
   • IV solutions are isotonic to avoid cell damage.

2. Saltwater Fish in Freshwater:

   • Higher solute concentration in fish cells than freshwater.
   • Water moves into fish cells, causing swelling and potential death.

3. Plants and Soil:

   • Water moves from saturated soil to plant roots due to higher solute concentration in roots.
   • Salting roads can create hypertonic soil, leading to plant dehydration.

4. Effect on Slugs:

   • Salt makes environment hypertonic, causing slug dehydration due to water movement out of cells.

Advanced Concepts

• Water Potential: In advanced biology, water travels to areas of lower water potential (lower free energy).
• Water loves solutes and avoids pressure.

Conclusion

• Understanding water movement is crucial in biology.
• Practice problems are available to test osmosis knowledge.
• Stay curious and explore more about osmosis.