Lipids serve a diverse array of functions inside the cell, ranging from
being energy sources to constructing the cell membrane. Lipids are made of fatty
acid molecules (e.g. palmitic acid, shown below) that consist two distinct
regions: a long hydrophobic hydrocarbon chain and a hydrophilic carboxylic acid
Fatty acids are a valuable food source. Each molecule of fatty
acid can be converted into twice the number of ATP molecules as glucose.
The most important function of fatty acid is its ability to
combine to form uniform bilayers of lipid (to prevent the hydrophobic region
from being exposed). These lipid bilayers are used to
form the impermeable cell membrane and helped
to define the first cell (see From
Molecules to the First Cell). The hydrophobic property of lipid membrane
also allows the cell to facilitate transport of molecules.