Hydrogen Bonds
💡 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.