Biochemistry: Importance of Water

Introduction to Water

• Water is an inorganic molecule and a solvent.
• Essential for many chemical reactions in living systems.

Unique Properties of Water

• Water is composed of one oxygen and two hydrogen atoms.
• Electronegativity:
  • Oxygen is electronegative, pulling electrons close.
  • Hydrogen is less electronegative, leading to partial charges.
• Charge Differential:
  • Partial negative charge on oxygen.
  • Partial positive charge on hydrogen.

Hydrogen Bonding

• Water molecules are attracted to each other through hydrogen bonds.
• These bonds, although weaker than covalent or ionic bonds, cause water molecules to be 'sticky'.

Comparison with Oil

• Water molecules are highly attracted to each other compared to nonpolar oil molecules that have Vander Waals forces.
• Water forms beads due to surface tension.

High Specific Heat Capacity

• Water has a high specific heat capacity due to hydrogen bonding.
• Phase Change:
  • Water requires more energy to change from liquid to gas compared to similar weight molecules like methane.
• Environmental Impact:
  • Oceans absorb and release heat, stabilizing Earth's temperature.
  • Water acts as a temperature buffer, supporting stable environments for life.

Importance of Water for Life

• Stability in temperatures aids in the survival and evolution of life.
• Water is a common factor considered in the search for life on other planets.

Ice Floating Phenomenon

• Ice floats because water molecules form crystals that are less dense than liquid water.
• Essential for aquatic life, preventing ecosystems from freezing.

Water as a Solvent

• Dissolves substances like sodium chloride due to its polar nature.
• Shell of Hydration:
  • Water molecules surround ions, pulling them into solution.
  • Dissolves many biological molecules (e.g., proteins, carbohydrates).

Illustration of Solvent Process

• A cartoon representation showing shells of hydration forming around ions.

Conclusion

• Water's properties make it indispensable for life and biochemical processes.
• Next topic: Organic molecules.