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Fatty acid

In chemistry, especially biochemistry, a fatty acid is an organic acid (or carboxylic acid), often with a long aliphatic tail (long chains), either saturated or unsaturated. Most of the natural fatty acid have a even number of carbon atoms, because they are made up of acetate which has two carbon atoms.

Industrially, fatty acids are produced by the hydrolysis of the ester linkages in a fat or biological oil (both of which are triglycerides), with the removal of glycerol. See oleochemicals.

Table of contents
1 Saturated
2 Unsaturated
3 Free Fatty Acids
4 pH


Saturated fatty acids are of the form

R-COH  , that is, R-COOH


R = CH3-(CH2)n

Saturated are:


Unsaturated fatty acids are of similar form, except that one or more alkene functional groups exist along the chain, substituting singly-bondeded


part of the chain with doubly-bonded


portions (this is, with carbons attached with a double bond to another carbon). In most of these, each double bond has 3n carbon atoms after it, for some n, and are all cis bonds.

There are two different ways to make clear were this double bonds are located in the molecule. For example:

Delta-9,12 or Δ9,12 : The double bond are the nineth and twelfth carbon-carbon bond counting from the end of the chain with the carboxyl group.

Omega-3 or Ω-3 : The first double bond is the third carbon-carbon bond counting from the end of the chain most distant from the carboxyl group. The next

Stearic and oleic acid are both 18 C fatty acids. They differ only in that stearic acid is saturated with H, while oleic acid is an unsaturated fatty acid (with two less H than the anterior).

Image.Several fatty acid molecules

Essential fatty acids or polyunsaturated fatty acids are fatty acids that are required in the human diet. This means they cannot be synthesized by the body and must be obtained from food. We can easily make saturated fatty acids and unsaturated fatty acids that have one double bond (monounsaturated fatty acids), but we do not have the proper enzymes to synthesis unsaturated fatty acids that have more than one double bond (polyunsaturated fatty acids).

These essential fatty acids are very important to our immune system and to help us regulate our blood pressure, for they are used to make essential compounds, such as prostaglandins.

Free Fatty Acids

Fatty acids not bound or attached to other molecules, like triglycerides or phospholipids.

The uncombined fatty acids or Free Fatty Acids may come from the breakdown of a triglyceride into its components (fatty acids and glycerol).

Free fatty acids are an important source of fuel for many tissues since they can yield relatively large quantities of ATP. Typically many cell types can use either glucose or fatty acids for this purpose. However, heart and skeletal muscle prefer fatty acids. On the other hand, brain cannot use fatty acids as a source of fuel, relying instead on glucose.


Long chain fatty acids do not have a pH. pH is a measure of acidity (or alkalinity) of an aqueous solution. Since long chain fatty acids are insoluble in water, it is difficult to measure their pH.

See also : triglycerides.