Almost everything water does for a cell traces back to one uneven molecule — and almost everything a cell is made of traces back to six elements.
Water is not special because it is wet. It is special because its electrons are shared unfairly and its shape refuses to cancel that out.
Oxygen's greater electronegativity pulls the shared pairs towards itself, leaving δ− on oxygen and δ+ on each hydrogen.
Lone pairs squeeze the two O–H bonds together. A linear molecule would cancel its dipoles; a bent one cannot.
One end of every water molecule is slightly negative and the other slightly positive — so molecules attract each other, end to end.
Tap each labelled part. The rest of the drawing fades so you can see what you have selected.
Tap the oxygen, a hydrogen, the bond angle, the covalent bonds, the dashed pink bond or the neighbouring molecule.
Five emergent properties, one cause. Switch between them and watch the same hydrogen bond do five different jobs.
Most of a living thing is built from six elements. Two of them are diagnostic: find nitrogen or phosphorus in a molecule and you have narrowed down what it can be.
Four covalent bonds per atom means chains, branches and rings — skeletons stable enough to hold a shape and varied enough to carry information.
Nitrogen sits in amino groups and nitrogenous bases. Phosphorus sits in phosphate groups: nucleotides, ATP and phospholipids.
Only two amino acids carry sulfur, but the disulfide bridges they form lock tertiary structure into place.
Tap a node to light up what it connects to. The pink dashed link is the one that pays off in later units.
Start at Polarity and work outward — every other node on this map is a consequence of it.
Drag a term into a gap, or tap a term and then tap a gap. Two terms belong nowhere.
Oxygen is more than hydrogen, so the shared electrons sit closer to the oxygen and the molecule ends up with at either end. Because the molecule is , those charges do not cancel out. A then forms between the δ+ hydrogen of one molecule and the δ− oxygen of another. Attraction between water molecules is ; attraction between water and a different polar surface is . Breaking those bonds soaks up energy, which is why water has a high . In ice each molecule is locked to four neighbours in an open lattice, so ice is than liquid water.
Single best answer. You get the reasoning as soon as you commit.