Lecture Notes: Water - The Essential Component of Life

Introduction

• Understanding life on Earth requires understanding water.
• Water was present at the beginning of life and remains the medium for life processes.

Structure of Water

• Composed of 3 atoms: 1 oxygen, 2 hydrogen.
• Water molecules are polar due to asymmetrical structure and polar covalent bonds.
  • Oxygen is more electronegative, causing partial charges.

Polarity and Hydrogen Bonds

• Polar nature leads to hydrogen bonds:
  • Oxygen's negative charge attracts hydrogen's positive charge of another water molecule.
• Hydrogen bonds are weak but crucial for many of water's properties.

Key Properties of Water

Cohesion

• Cohesion: Water molecules stick to each other due to hydrogen bonds.
  • Crucial in biological systems, e.g., water transport in plants via xylem.
  • Enables phenomena like transpiration and surface tension.

Adhesion

• Adhesion: Water molecules stick to other surfaces.
  • Important in soil moisture and plant xylem function.
  • Capillary action in soil and plants, aiding in water absorption.

Solvent Properties

• Water is a universal solvent; dissolves many substances, supporting biological processes.
  • Metabolism and nutrient transport in organisms.
  • Hydrophilic substances dissolve well; nonpolar substances do not.
  • Example: Phospholipid membranes in cells.

Physical Properties

Specific Heat

• High specific heat: Water requires more energy to change temperature.
  • Stabilizes environments and body temperatures.

Thermal Conductivity

• High ability to transfer heat.
  • Important for temperature regulation in organisms, e.g., fennec foxes.

Buoyancy

• Ability to float based on density comparison.
  • Influences organisms like green algae and their position in water.

Viscosity

• Low viscosity: Water flows easily, but increases with added solutes.
  • Important for organisms in ocean water.

Comparative Organism Examples

• Black-throated Loon (Gavia Arctica) and Ringed Seal (Pusa hispira).
  • Both rely on different physical properties of water due to their habitats.
  • The seal's adaptations for moving in water: thicker fur for heat retention.
  • Understand comparisons for exams and application to other organisms.

Conclusion

• Water's unique properties are fundamental to life processes.
• Essential to study its role in various biological systems for a deeper understanding.