Skip to main content
Select Source:

fatty acids

fatty acids Organic acids consisting of carbon chains with a carboxyl group at the end. The nutritionally important fatty acids have an even number of carbon atoms, commonly between twelve and twenty‐two.

Saturated fatty acids are those in which every carbon atom carries its full ‘quota’ of hydrogen atoms, and therefore there are only single bonds between adjacent carbon atoms.

Unsaturated fatty acids have one or more carbon‐carbon double bonds in the molecule. Chemically these double bonds can take up hydrogen, which is the process of hydrogenation, forming saturated fatty acids. Fatty acids with only one double bond are termed mono‐unsaturated, oleic acid is the main one in fats and oils. Fatty acids with two or more double bonds are polyunsaturated fatty acids, often abbreviated to pufa.

Unsaturated fatty acids lower levels of cholesterol in the blood, while saturated fatty acids raise it. To reduce the risk of heart disease, it is recommended that saturated fatty acid intake should not exceed about 10% of energy.

In general fats from animal sources are high in saturated and relatively low in unsaturated fatty acids; vegetable and fish oils are generally higher in unsaturated and lower in saturated fatty acids.

In addition to their accepted names, fatty acids can be named by a shorthand giving the number of carbon atoms in the molecule (e.g. C18), then a colon and the number of double bonds (e.g. C18 : 2), followed by the position of the first double bond from the methyl end of the molecule as n‐ or ω (e.g. C18 : 2 n‐6, or C18 : 2 ω6).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acids." A Dictionary of Food and Nutrition. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acids." A Dictionary of Food and Nutrition. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/fatty-acids

"fatty acids." A Dictionary of Food and Nutrition. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/fatty-acids

fatty acids

fatty acids are a constituent of dietary fat and important components of the body's phospholipids and glycolipids (e.g. in cell membranes, lung surfactant, the nervous system). They consist of long carbon chains, each with a carboxyl group at one end. If the chain contains double bonds the fatty acids are said to be polyunsaturated; when no double bonds are present the fatty acid is saturated. Examples of saturated and unsaturated fatty acids are palmitic acid and linoleic acid, with 16 carbons and no double bonds, and 18 carbons with three double bonds, respectively. Fatty acids form esters with alcohols, and the common esters are glycerides, because the alcohol involved is glycerol. As glycerol has three alcoholic groups, most fats are triglycerides, and this is the major form of energy storage.

Fatty acids are absorbed from the gut as products of fat digestion, or made in the body from the other forms in which fats are absorbed. They are a major fuel for energy production at any time, except after a carohydrate-rich meal, and they are the main nutrient mobilized from fat stores in prolonged exercise. There are several essential polyunsaturated fatty acids which must be obtained from the diet for the synthesis of vital substances.

Alan W. Cuthbert


See cell membrane; exercise; fats; metabolism.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acids." The Oxford Companion to the Body. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acids." The Oxford Companion to the Body. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/fatty-acids

"fatty acids." The Oxford Companion to the Body. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/fatty-acids

fatty acid

fatty acid An organic compound consisting of a hydrocarbon chain and a terminal carboxyl group (see carboxylic acids). Chain length ranges from one hydrogen atom (methanoic, or formic, acid, HCOOH) to nearly 30 carbon atoms. Ethanoic (acetic), propanoic (propionic), and butanoic (butyric) acids are important in metabolism. Long-chain fatty acids (more than 8–10 carbon atoms) most commonly occur as constituents of certain lipids, notably glycerides, phospholipids, sterols, and waxes, in which they are esterified with alcohols. These long-chain fatty acids generally have an even number of carbon atoms; unbranched chains predominate over branched chains. They may be saturated (e.g. palmitic acid and stearic acid) or unsaturated, with one double bond (e.g. oleic acid) or two or more double bonds, in which case they are called polyunsaturated fatty acids (e.g. linoleic acid and linolenic acid). See also essential fatty acids.

The physical properties of fatty acids are determined by chain length, degree of unsaturation, and chain branching. Short-chain acids are pungent liquids, soluble in water. As chain length increases, melting points are raised and water-solubility decreases. Unsaturation and chain branching tend to lower melting points.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." A Dictionary of Biology. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." A Dictionary of Biology. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid-2

"fatty acid." A Dictionary of Biology. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid-2

fatty acid

fatty acid, any of the organic carboxylic acids present in fats and oils as esters of glycerol. Molecular weights of fatty acids vary over a wide range. The carbon skeleton of any fatty acid is unbranched. Some fatty acids are saturated, i.e., each carbon atom is connected to its carbon atom neighbors by single bonds; and some fatty acids are unsaturated, i.e., contain at least one carbon-carbon double bond (see chemical bond). When fats and oils are hydrolyzed with an alkali, the fatty acids are liberated as their metal salts; these salts are soaps. Butyric acid is a fatty acid found in butter.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/fatty-acid

"fatty acid." The Columbia Encyclopedia, 6th ed.. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/fatty-acid

fatty acid

fatty acid A long-chained, predominantly unbranched, carboxylic acid, in which a side-chain of carbon atoms is attached to the carboxyl group, and hydrogen atoms to some or all of the carbon atoms in the side-chain. There is usually an odd number of carbon atoms in the chain, commonly 15 or 17. If the carbon atoms of the side-chain carry as many hydrogen atoms as they are capable of carrying the fatty acid is said to be saturated; if there are fewer than the maximum possible number of hydrogen atoms it is unsaturated; if more than two sites on the chain are unsaturated it is polyunsaturated.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." A Dictionary of Plant Sciences. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." A Dictionary of Plant Sciences. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid-0

"fatty acid." A Dictionary of Plant Sciences. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid-0

fatty acid

fatty acid A long-chained, predominantly unbranched, carboxylic acid; it may be saturated or unsaturated. The side chains usually have an odd number (commonly 15 or 17) of carbon atoms to which hydrogen atoms may be attached; if all available hydrogen sites are occupied the fatty acid is said to be saturated, if one or more sites is vacant it is unsaturated, and if two or more sites are vacant it is polyunsaturated. Fatty acids have the general formula R—COOH, where R is hydrogen or a group of hydrogen and carbon atoms; saturated fatty acids have the general formula CnH2n+1COOH.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." A Dictionary of Zoology. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." A Dictionary of Zoology. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid-1

"fatty acid." A Dictionary of Zoology. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid-1

fatty acids

fatty acids Organic compound consisting of a carboxylic acid group (–COOH) bound to a hydrocarbon chain. Examples of saturated fatty acids (those with only single bonds in their hydrocarbon chain) are acetic acid and palmitic acid; unsaturated fatty acids (one double bond) include oleic acid; polyunsaturated fatty acids (two or more double bonds) include linoleic acid. Essential fatty acids (EFAs) are polyunsaturated fats that are essential to the human diet because they cannot be manufactured by the body.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acids." World Encyclopedia. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acids." World Encyclopedia. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/fatty-acids

"fatty acids." World Encyclopedia. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/fatty-acids

fatty acid

fatty acid (fat-i) n. an organic acid such as oleic acid or stearic acid. Fatty acids are the fundamental constituents of many important lipids, including triglycerides. Some fatty acids can be synthesized by the body; others (see essential fatty acid) must be obtained from the diet. See also fat.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." A Dictionary of Nursing. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." A Dictionary of Nursing. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid

"fatty acid." A Dictionary of Nursing. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid

fatty acid

fatty acid Long-chained, predominantly unbranched, carboxylic acid; it may be saturated or unsaturated. Fatty acids have the general formula R-(CH2)n-COOH, where R represents a hydrocarbon group, e.g. CH3 or C2H5 and n is any whole number between 1 and 16.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." A Dictionary of Earth Sciences. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." A Dictionary of Earth Sciences. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid

"fatty acid." A Dictionary of Earth Sciences. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid

fatty acid

fat·ty ac·id • n. Chem. a carboxylic acid consisting of a hydrocarbon chain and a terminal carboxyl group, esp. any of those occurring as esters in fats and oils.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"fatty acid." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 24 Jun. 2017 <http://www.encyclopedia.com>.

"fatty acid." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (June 24, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid

"fatty acid." The Oxford Pocket Dictionary of Current English. . Retrieved June 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/fatty-acid