Water and macromolecules – polarity and hydrogen bonding
BiologyCell BiologyAges 15–16
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Cell Biology
The water mode draws polar H₂O molecules with an oxygen end carrying a partial negative charge and two hydrogen ends carrying a partial positive charge, shows hydrogen bonds as dashed lines and continuously counts the average number of bonds per molecule; cooling below 0 °C locks molecules into an ice lattice with greater spacing (so ice floats), heating to 100 °C breaks all hydrogen bonds as the water evaporates, and adding salt or sugar shows water molecules surrounding and dissolving them, while oil stays undissolved. The macromolecule mode shows how monomers of carbohydrates, lipids, proteins and nucleic acids link into chains.
Lesson: Chemical elements, water and biological macromolecules
What it shows
Water molecules are polar: the oxygen atom carries a partial negative charge and the hydrogen atoms a partial positive charge, so neighbouring molecules attract one another through hydrogen bonds. These bonds explain water's high specific heat capacity, surface tension and cohesion, and its role as a solvent for ions and polar molecules, while non-polar oils do not dissolve. In ice each molecule holds four hydrogen bonds in an open lattice, making ice less dense than liquid water. A second mode shows the four classes of biological macromolecules and how their monomers join by condensation reactions that release water.
How to use
In water mode, drag the Water temperature from below 0 °C to above 100 °C and watch the average number of hydrogen bonds per molecule and the change of state. Change the Substance added to water to compare table salt, glucose and cooking oil. Then press View macromolecules and step through each Macromolecule to view, noting its monomer, the type of bond that links monomers and typical examples.
Parameters you can change
- Content Water and hydrogen bonding, Four macromolecule classes
- Water temperature -20–110 °C
- Substance added to water Nothing added, Table salt NaCl (polar), Glucose sugar (polar), Cooking oil (non-polar)
- Macromolecule to view Carbohydrate – glucose monomer, Lipid – glycerol and fatty acids, Protein – amino acid monomer, Nucleic acid – nucleotide monomer
- Number of water molecules shown 12–60 molecules
Questions to explore
- How does the average number of hydrogen bonds per molecule change as ice is heated to vapour?
- Why do salt and glucose dissolve in water while cooking oil stays as a separate layer?
- Which of the four macromolecule classes is not built from a single repeating monomer?
