Lipids

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 group.

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.