Fatty Acids: Structures and Properties

Abstract

Fatty acids play a key role in metabolism: as a metabolic fuel, as a necessary component of all membranes, and as a gene regulator. In addition, fatty acids have a number of industrial uses.

Keywords: biological effects; eicosanoids; requirements; polyunsaturated fatty acids; diet; peroxidation

Figure 1.

Nomenclature for fatty acids. Fatty acids may be named according to systematic or trivial nomenclature. One systematic way to describe fatty acids is related to the methyl (ω) end. This is used to describe the position of double bonds from the end of the fatty acid. The letter n is also often used to describe the ω position of double bonds.

Figure 2.

Structure of different unbranched fatty acids with a methyl end and a carboxyl (acidic) end. Stearic acid is a trivial name for a saturated fatty acid with 18 carbon atoms and no double bonds (18:0). Oleic acid has 18 carbon atoms and one double bond in the ω‐9 position (18:1 ω‐9), whereas eicosapentaenoic acid (EPA), with multiple double bonds, is represented as 20:5 ω‐3. This numerical scheme is the systematic nomenclature most commonly used. It is also possible to describe fatty acids systematically in relation to the acidic end of the fatty acids; symbolized Δ (Greek delta) and numbered 1. All unsaturated fatty acids are shown with cis configuration of the double bonds. DHA, docosahexaenoic acid.

Figure 3.

Synthesis of ω‐3 and ω‐6 polyunsaturated fatty acids (PUFAs). There are two families of essential fatty acids that are metabolized in the body as shown in this figure. Retroconversion, e.g. DHA→EPA also takes place.

Figure 4.

Metabolism of fatty acids. Free fatty acids (FFA) are taken up into cells mainly by protein carriers in the plasma membrane and transported intracellularly via fatty acid‐binding proteins (FABP). FFA are activated (acyl‐CoA) before they can be shuttled via acyl‐CoA binding protein (ACBP) to mitochondria or peroxisomes for β‐oxidation (formation of energy as ATP and heat), or to endoplasmic reticulum for esterification to different lipid classes. Acyl‐CoA or certain FFA may bind to transcription factors that regulate gene expression or may be converted to signalling molecules (eicosanoids). Glucose may be transformed to fatty acids if there is a surplus of glucose/energy in the cells.

Figure 5.

Mechanisms of action for fatty acids. Thromboxanes formed in blood platelets promote aggregation (clumping) of blood platelets. Leukotrienes in white blood cells act as chemotactic agents (attracting other white blood cells). See Figure .

Figure 6.

Synthesis of eicosanoids from Arachidonic acid or eicosapentaenoic acid (EPA).

Figure 7.

Biological effects of eicosanoids derived from Arachidonic acid (AA; 20:4 ω‐6) or eicosapentaenoic acid (EPA; 20:5 ω‐3). TX, thromboxane; PG, prostaglandin, LT, leukotriene.

Figure 8.

Advice for dietary lipid sources and amounts.

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References

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Further Reading

Das UN, Ramos EJ and Meguid MM (2003) Metabolic alterations during inflammation and its modulation by central actions of omega‐3 fatty acids. Current Opinion in Clinical Nutrition and Metabolic Care 6: 413–419.

Drevon CA, Nenseter MS, Brude IR et al. (1995) Omega‐3 fatty acids – nutritional aspects. Canadian Journal of Cardiology 11 (supplement G): 47–54.

Duttaroy AK and Spener F (eds) (2003) Cellular Proteins and Their Fatty Acids in Health and Disease. Weinheim: Wiley–VCH.

Gurr MI and Harwood JL (1991) Fatty acid structure and metabolism. In: Gurr MI and Harwood JL (eds) Lipid Biochemistry, An Introduction. London: Chapman and Hall.

Harris WS, Park Y and Isley WL (2003) Cardiovascular disease and long‐chain omega‐3 fatty acids. Current Opinion in Lipidology 14: 9–14.

Helland I, Smith L, Saarem K, Saugstad OD and Drevon CA (2003) Maternal supplementation with very long‐chain n‐3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age. Pediatrics 111: E39–E44.

Kris‐Etherton PM, Harris WS and Appel LJ (2003) Nutrition Committee. Fish consumption, fish oil, omega‐3 fatty acids, and cardiovascular disease. Arteriosclerosis Thrombosis and Vascular Biology 23: e20–30.

Nenseter MS and Drevon CA (1996) Dietary polyunsaturates and peroxidation of low‐density lipoproteins. Current Opinion in Lipidology 7: 8–13.

Storlien L, Hulbert AJ and Else PL (1998) Polyunsaturated fatty acids, membrane function and metabolic diseases such as diabetes and obesity. Current Opinion in Clinical Nutrition and Metabolic Care 1: 559–563.

Terry PD, Rohan TE and Wolk A (2003) Intakes of fish and marine fatty acids and the risks of cancers of the breast and prostate and of other hormone‐related cancers: a review of the epidemiologic evidence. American Journal of Clinical Nutrition 77: 532–543.

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Rustan, Arild C, and Drevon, Christian A(Sep 2005) Fatty Acids: Structures and Properties. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003894]