Fatty Acids

Long-chain carboxylic acids that have an even number (usually 12-18) of carbon atoms.

Insoluble in water. Saturated or unsaturated.

Fatty Acids

Fatty acids

Fatty Acid Formulas

The formulas for fatty acids are written as

condensed and line-bond formulas.

For example fatty acid with 8 carbon atoms can

be written as:

CH3—(CH2)6—COOH

CH3—CH2—CH2—CH2—CH2—CH2—CH2—COOH

O ||

CH3—CH2—CH2—CH2—CH2—CH2—CH2—C—OH

OH

O

General nomenclature

The carbon atoms of an acid are numbered (or lettered with Greek lettering system, such as α, β, γ) either from the carboxyl group or from the carbon farthest removed from the carboxyl group (n or omega numbering system)

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

10 9 8 7 6 5 4 3 2 1

1 2 3 4 5 6 7 8 9 10

ω δ γ β α

Systematic names

Saturated F.As.Saturated fatty acids have single C–C bonds.

Saturated fatty acids have: Molecules that fit closely together

in a regular pattern. Strong attractions between fatty

acid chains. High melting points that makes

them solids at room temperature.

Saturated F.As.

Unsaturated fatty acids have cis C=C bonds.

Unsaturated F.As.

Unsaturated fatty acids typically contain cis double bonds.

Unsaturated F.As.

Unsaturated fatty acids: Have nonlinear chains that do not allow molecules

to pack closely. Have low melting points. Are liquids at room temperature.

Unsaturated F.As.

Olive Oil

Olive oil contains a high percentage of oleic acid.

Oleic acid is a monounsaturated fatty acid with one cis double bond.

In a triacylglycerol, glycerol forms ester bonds with three fatty acids.

Triacylglycerols

Hydrogenation of Oils

Hydrogenation: Adds hydrogen

to double bonds in oils to form single bonds.

Produces solid shortening, margarine, and other products.

Omega-6 and Omega-3 F.As.

The first double bond: At carbon 6 (omega-6) (e.g. vegetable oils) At carbon 3 (omega-3) (e.g. fish oils)

Essential fatty acids

Mammals cannot synthesize the two main types of polyunsaturated fatty acids: the linoleic (omega-6) and linolenic (omega-3)

Essential fatty acid deficiency is characterized by dermatitis and poor wound healing

Most prostaglandins are synthesized from arachidonic acid (a linoleic acid derivative)

Lack of these prostaglandins causes some aspects of the essential fatty acid deficiency syndrome

Essential fatty acids

A small daily intake of linolenic acid is recommended (this may be especially important when the nervous system is developing)

Docosahexaenoic acid (22:6 3,6,9,12,15,18) is needed for maximum development of the visual and central nervous systems during the neonatal period (it is present in large amounts in the retina and parts of the brain; it enhances the visual response and the function of certain domains in neural membranes)

Prostaglandins

Prostaglandins have: 20 carbon atoms in their fatty acid chains. An OH on carbon 11 and 15. A trans double bond at carbon 13.

Prostaglandins in the Body

Prostaglandins are:

Produced by injured tissues.

Involved in pain, fever, and inflammation.

Not produced when anti-inflammatory drugs such as aspirin inhibit their synthesis.

Other eicosanoids

When a cell responds to a stimulus, bioactive mediators (prostaglandins, thromboxanes, leukotrienes, and others) often are formed from the lipids contained in its membranes.

Thromboxanes regulate blood coagulation.

Leukotrienes play a role in allergic and inflammation responses. They were isolated from leukocytes (white blood cells).