Triglicerides and fatty acids

Phospholipids and cell membranes

Sterols: cholesterol and testosterone


Extra topics:

Fuel made from fat: Biodiesel

Eating fat without gaining weight:Olestra

Trans fats




Lipids (or fats)


The phospholipid is a trigliceride where one of the fatty acids are replaced by a molecule containing a phosphate group. The polarity added by the presence of the phosphate makes the lipid highly hydrophilic at this end.

A phospholipid

The combination of hydrophilicity at one end and hydrophobicity at the other (hydrocatrbon chain) makes phospholipids suitable for the formation of cell membranes (below), and also other strucures like micelles and lipossomes. The cell membrane is extremely thin, having only a few nm across. Its structure has similarities to the soap bubble (the cell membrane is obviously much more complex).


Cell membrane, showing the hydrophilic tail ends in contact with the interior and exterior of the cell and the hydrophobic parts froming the inside of the membrane


The cell membrane encloses the cell. It includes various proteins, each having a different role to perform. It is very important to promote and control the flux of ions in and out of the membrane. Other substances also have to circulate through the membrane to allow for the functioning of the cell.

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