General Index


Neutral Lipids

Neutral Lipids are esters of fatty acid(s) with an alcohol.

In Biochemistry are particularly important the esters of fatty acids with the polyalcohol Glycerol.

Glycerol has no asymmetric carbons, but when sterified, carbon 2 may become asymmetric. For this reason we adopt in glycerol the sn- convention:


If we see the molecule with carbon 2 (sn-2) in the same configuration as L-Glyceraldehyde, sn-1 carbon will be up and sn-3 down. Its structure in the Fischer projection would be:

Esters of fatty acids with glycerol are called Acylglycerols or Glycerides. Depending on the number of fatty acids esterified, we have the Monoacylglycerols or Monoaglycerides when only one of the alcohols appears esterified. The structure of sn-1 palmitoyl glycerol is:






If there are two alcoholic positions esterified to fatty acids, we get the Diacylglycerols of Diglycerides. The structure of sn-1 palmitoyl sn-2 linoleoyl glycerol is as follows:






Having one or two free alcoholic groups, mono- and diacylglycerols have a certain polar character: They are amphipathic molecules.

When the three positions of glycerol appear esterified, we have the Triacylglycerols or Triglycerides. This is the structure of sn-1 palmitoyl sn-2 linoleoyl sn-3 lauroyl glycerol:






Triacylglycerols are by far the most abundant neutral lipids in biological media, where they have a function of energy reserve, and are stored in the adipose tissue in Animals and in the seeds of some Plants (olive, sunflower, soja, etc.). They are strongly hydrophobic, not having free polar groups.


Other neutral lipids are the Waxes, resulting from the esterification of a fatty acid with a fatty alcohol, that is, a long-chain aliphatic alcohol. We present the structure of Cetyl palmitate, ester of palmitic acid (C16) with cetyl alcohol (an alcohol of 16 carbon atoms).



Waxes are completely hydrophobic and have a function of protection of epithelia. They are very unreactive from a chemical point of view. Cetyl palmitate is the main component of Whale sperm.


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