Makindo Medical Notes

💡 About Hydrogen Bonds

• ⚖️ Strength: Hydrogen bonds (10–40 kJ/mol) are much weaker than covalent bonds (~400 kJ/mol), but collectively they have a major stabilising effect in biology.
• 🧩 Proteins: They are critical in maintaining tertiary (3D folding) and quaternary (subunit interactions) structures of proteins.
• 🧬 DNA: Hydrogen bonds hold complementary bases together in the double helix:
  • A–T pairs → 2 hydrogen bonds
  • C–G pairs → 3 hydrogen bonds (stronger, so C–G rich DNA is more stable)
• 💧 Water Properties: Hydrogen bonds are responsible for many unique properties of water:
  • Keep water liquid at room temperature (otherwise it would be a gas like H₂S).
  • Make ice less dense than water → ice floats, insulating aquatic life in winter.
  • High specific heat capacity → buffers temperature changes in organisms and environments.
  • High surface tension → allows capillary action and supports small organisms on water surfaces.
• 🌍 Biological Importance: Hydrogen bonds underpin enzyme–substrate recognition, antibody–antigen binding, and receptor–ligand interactions.

📌 Summary

Hydrogen bonds are weak individually but powerful in numbers. They stabilise proteins 🧩, hold DNA strands together 🧬, and give water 💧 its life-sustaining properties. Without them, biology as we know it could not exist.