On Food and Cooking

performed mainly by phospholipids similar to
lecithin (p. 802), molecules that cooks also
use to form membranes around tiny oil
droplets. Fats and oils themselves are created
and stored by animals and plants as a
concentrated, compact form of chemical
energy, packing twice the calories as the same
weight of either sugar or starch.
In addition to fats, oils, and phospholipids,
the lipid family includes betacarotene and
similar plant pigments, vitamin E, cholesterol,
and waxes. These are all molecules made by
living things that consist mainly of chains of
carbon atoms, with hydrogen atoms projecting
from the chain. Each carbon atom can form
four bonds with other atoms, so a given
carbon atom in the chain is usually bonded to
two carbon atoms, one on each side, and two
hydrogens.
This carbon-chain structure has one
overriding consequence: lipids can’t dissolve
in water. They are “hydrophobic” or “water-