Phospholipids

Phospholipids are an important subgroup of lipid. They are a vital component of membranes.

Phospholipids are:

• the most highly charged of the lipids because of the presence of the phosphate group (also they often have other charged groups at the phosphate end of the molecule)
• the other end of the phospholipid molecule is very similar to triglyceride - comprising of long hydrocarbon sequences of fatty acyl groups
• the structure of phospholipids mean that one end of the molecule orients itself towards non-polar substances (generally other lipids) and the other end of the molecule seeks water - this orientation effect is essential for the role of phospholipids in membranes and lipoproteins

Phospholipids can be divided into glycerophospholipids and phosphosphingolipids.

The glycerophospholipids consist of diacylglycerol, phosphoric acid and another specified alcohol. The phosphoric acid molecule forms ester bonds with the other two constituents.

Examples include, according to the respective alcohol:

• phosphatidyl choline, also termed lecithin
• phosphatidyl inositol
• phosphatidyl serine
• phosphatidyl ethanolamine

Examples of phosphosphingolipids include sphingomyelin. These tend to be concentrated in neurons. They are a result of a phosphate esterification of the long chain amino alcohol sphingosine with a glycerophospholipid.