Water and macromolecules – polarity and hydrogen bonding

BiologyCell BiologyAges 15–16

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.