FoundationalConceptsNeuroscience

from the end of the hydrocarbon chain, a so-called omega-9 fatty acid.

O

FP OH

Oleic acid

Because lipids are composed primarily of carbon and hydrogen
atoms, they are largely hydrophobic in nature, preferring the com-
pany of other lipids rather than that of water. Lipophilic (lipid loving)
is synonymous with hydrophobic. And conversely, lipophobic (lipid
fearing) means the same as hydrophilic. Oil and water don’t mix.
Of great importance in living organisms are the phospholipids.
These lipids are composed of two carbon-hydrogen chains (each chain
generally sixteen to twenty-four carbons in length), joined together
at one end by a group of atoms containing, in addition to the ubiq-
uitous carbons and hydrogens, atoms of oxygen, phosphorus, and
perhaps nitrogen. These latter atoms form bonds having polarity and
sometimes even electric charge. Thus, phospholipids have a highly
hydrophilic portion (the polar or electrically charged phosphorus-con-
taining “head group”) and a highly hydrophobic portion (the two long
nonpolar hydrocarbon chains, or “tail groups”).
Among the most abundant phospholipids in the cells of animals
and plants are the phosphatidylcholines, an example of which is
shown here: