Phospholipid

Phospholipids are a class of lipids that are a major component of all cell membranes. They can form lipid bilayers because of their amphiphilic characteristic. The structure of the phospholipid molecule generally consists of two hydrophobic fatty acid "tails" and a hydrophilic "head" consisting of a phosphate group. The two components are joined together by a glycerol molecule. The phosphate groups can be modified with simple organic molecules such as choline.

Structure

The 'head' of a phospholipid is made from a glycerol molecule. To the glycerol backbone is attached two fatty acid molecules are attached as 'tails'. The 'head' is also attached to a phosphate group, which is modified by an alcohol. The 'tails' are hydrophobic, avoiding water (lipophobic), and the 'head' is hydrophilic, making it compatible with water.

Functions

Phospholipids are one of the components of lipid bilayers. A lipid bilayer is a powerful barrier to most molecules and ions. This allows a cell to regulate the molecules and ions within the cell, including such vital functions as the transport of nutrients into the cell and the removal of waste products.

Phospholipids are also involved in signal transduction, as they can be modified by enzymes to serve as secondary messengers. In addition, phospholipids are involved in membrane fusion and vesicular trafficking.

See also

• Lipid bilayer
• Cell membrane
• Signal transduction
• Membrane fusion
• Vesicular trafficking

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