Lecture on Water and Biological Systems

Introduction

• Discussion on student performance in IB Biology.
• Encouragement to focus more on summative exam preparations.

Importance of Water in Biological Systems

• Water as a Solvent:
  • Water is a polar molecule with positive and negative ends.
  • Allows it to dissolve many substances (universal solvent).
  • Important in biological systems.

Properties of Water

• Polarity and Dissolution:
  • Water molecules surround substances like ions or molecules (e.g., sodium, glucose) based on charge attractions or hydrogen bonds.
  • Dissolves polar molecules and charged atoms easily.

Water Molecule Interactions

• Hydrogen Bonding:
  • Water molecules stick together via hydrogen bonds.
  • Hydrogen bonds are constantly broken and reformed.

Solvation Process

• Water molecules move to encapsulate solutes.
• Attraction to solutes is stronger than to other water molecules.

Osmosis and Cell Behavior

• Osmosis:
  • Water moves from areas of low solute concentration to high solute concentration.
  • Terms:
    • Hypotonic: Low solute concentration.
    • Hypertonic: High solute concentration.
    • Isotonic: Equal solute concentration.
  • Net movement of water is called osmosis.

Implications for Cells

• In Animal and Plant Cells:
  • Plant cells withstand more osmotic pressure due to cell walls.
  • Animal cells may burst in hypotonic solutions.
  • Hypertonic solutions cause shrinking and crenation.

Experiments and Applications

• Osmosis Experiments:

  • Use of potatoes to demonstrate osmosis.
  • Importance of calculating standard deviation and error.

• Medical and Scientific Applications:

  • Transport and preservation of organs using isotonic solutions (normal saline).
  • IV solutions are isotonic to human blood to maintain balance.

Conclusion

• Understanding water movement is crucial for biology and medical applications.
• Encouragement to explore osmosis and water's role in living systems further.