Fatty Acids

A fatty acid is a combination of a chain of carbon and hydrogenatoms, known as a hydrocarbon, and a particular acid group known as a carboxyl group (-COOH). Three fatty-acid molecules combined with a glycerol form a triglyceride fat or oil.

While several varieties of fatty acid occur in nature, all belong in one of two categories—saturated or unsaturated. In a saturated fatty-acid molecule, all the carbon atoms in the chain are attached to two hydrogen atoms, the maximum amount. All the bonds between the carbon atoms in the chain are single electron bonds. An example of fat made of saturated fatty acids is butter.

Unsaturated fatty-acid molecules have one or more carbon atoms with only a single hydrogen atom attached. In these chains, one or more bonds between the carbon atoms are double. A molecule with one double bond is called monounsaturated, and two or more double bonds is called polyunsaturated. An example of unsaturated fat is vegetable oil.

Generally, fats consisting of saturated fatty acids are solid, and those made up of unsaturated molecules are liquid. An unsaturated fatty acid may be converted into saturated through a process called hydrogenation. While most modern diets are aimed at the reduction of fatty acids (fats), it is important to recognize that several of them, such as oleic, butyric, and palmitic acid, are important parts of the human diet. Another, linoleic acid, is absolutely essential to human life. It is an important part of a vital chemical reaction in the body, and is obtained solely through ingestion. It is found in corn, soybean, and peanut oils.

Recently, concern about the amount of trans fatty acids present in food has caused debate. Trans fatty acids are formed during the process of partial hydrogenation of unsaturated fatty acids (like vegetable oil) into margarine and vegetable shortening. Some research suggests that levels of trans fatty acids can alter the amount of cholesterol found in blood, which can be a significant risk to people suffering from high cholesterol levels and heart disease. In addition to being found in margarine, trans fatty acids are also found naturally in small quantities in beef, pork, lamb, and milk. There is conflicting evidence, however, of the dangers of trans fatty acids in daily diets. Generally, it is recommended to limit the total daily amount of fat eaten, rather than focusing solely on trans fatty acid consumption. In some countries such as Canada, legislation has been enacted to limit or ban outright the use of trans fats in certain processed foods such as potato chips and cookies.

Fatty acids

A fatty acid is a combination of a chain of carbon and hydrogen atoms , known as a hydrocarbon , and a particular acid group (-COOH). Three fatty-acid molecules combined with a glycerol form a triglyceride fat or oil.

While several varieties of fatty acid occur in nature, all belong in one of two categories—saturated or unsaturated. In a saturated fatty-acid molecule , all the carbon atoms in the chain are attached to two hydrogen atoms, the maximum amount. All the bonds between the carbon atoms in the chain are single electron bonds. An example of fat made of saturated fatty acids is butter.

Unsaturated fatty-acid molecules have one or more carbon atoms with only a single hydrogen atom attached. In these chains, one or more bonds between the carbon atoms are double. A molecule with one double bond is called monounsaturated, and two or more double bonds is called polyunsaturated. An example of unsaturated fat is vegetable oil.

Generally, fats consisting of saturated fatty acids are solid, and those made up of unsaturated molecules are liquid. An unsaturated fatty acid may be converted into saturated through a process called hydrogenation . While most modern diets are aimed at the reduction of fatty acids (fats), it is important to recognize that several of them, such as oleic, butyric, and palmitic acid, are important parts of the human diet. Another, linoleic acid, is absolutely essential to human life. It is an important part of a vital chemical reaction in the body, and is obtained solely through ingestion. It is found in corn, soybean , and peanut oils.

Recently, concern about the amount of trans fatty acids present in food has caused debate. Trans fatty acids are formed during the process of partial hydrogenation of unsaturated fatty acids (like vegetable oil) into margarine and vegetable shortening. Some research suggests that levels of trans fatty acids can alter the amount of cholesterol found in blood , which can be a significant risk to people suffering from high cholesterol levels and heart disease . In addition to being found in margarine, trans fatty acids are also found naturally in small quantities in beef, pork, lamb, and milk. There is conflicting evidence, however, of the dangers of trans fatty acids in daily diets. Generally, it is recommended to limit the total daily amount of fat eaten, rather than focusing solely on trans fatty acid consumption.

See also Carboxylic 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).

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

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.