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A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an
ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glyceride ...
derived from
glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
and three
fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
(from ''
tri- Numeral or number prefixes are prefixes derived from numerals or occasionally other numbers. In English and many other languages, they are used to coin numerous series of words. For example: * unicycle, bicycle, tricycle (1-cycle, 2-cycle, 3-cy ...
'' and ''
glyceride Glycerides, more correctly known as acylglycerols, are esters formed from glycerol and fatty acids, and are generally very hydrophobic. Glycerol has three hydroxyl functional groups, which can be esterified with one, two, or three fatty acids ...
''). Triglycerides are the main constituents of body fat in humans and other vertebrates, as well as vegetable fat. They are also present in the blood to enable the bidirectional transference of
adipose Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular e ...
fat and blood glucose from the liver, and are a major component of human skin oils. Many types of triglycerides exist. One specific classification focuses on saturated and unsaturated types.
Saturated fat A saturated fat is a type of fat in which the fatty acid chains have all single bonds. A fat known as a glyceride is made of two kinds of smaller molecules: a short glycerol backbone and fatty acids that each contain a long linear or branched c ...
s have ''no'' C=C groups;
unsaturated fat An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond ...
s feature one or more C=C groups. Unsaturated fats tend to have a lower
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depe ...
than saturated analogues; as a result, they are often
liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...
at room temperature.


Chemical structure

Triglycerides are tri-
ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glyceride ...
s consisting of a
glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
bound to three
fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...
molecules.
Alcohols In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...
have a hydroxyl (HO–) group. Organic acids have a carboxyl (–COOH) group. Alcohols and organic acids join to form esters. The glycerol molecule has three hydroxyl (HO–) groups and each fatty acid has a carboxyl group (–COOH). In triglycerides, the hydroxyl groups of the glycerol join the carboxyl groups of the fatty acid to form ester bonds: :HOCH2CH(OH)CH2OH + RCO2H + R′CO2H + R″CO2H → RCO2CH2CH(O2CR′)CH2CO2R″ + 3H2O The three fatty acids (RCO2H, R′CO2H, R″CO2H in the above equation) are usually different, as many kinds of triglycerides are known. The chain lengths of the fatty acids in naturally occurring triglycerides vary, but most contain 16, 18, or 20 carbon atoms. Natural fatty acids found in plants and animals are typically composed of only even numbers of carbon atoms, reflecting the pathway for their biosynthesis from the two-carbon building-block acetyl CoA. Bacteria, however, possess the ability to synthesise odd- and branched-chain fatty acids. As a result,
ruminant Ruminants ( suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...
animal fat contains odd-numbered fatty acids, such as 15, due to the action of bacteria in the
rumen The rumen, also known as a paunch, is the largest stomach compartment in ruminants and the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. The rumen's microbial favoring environment allows ...
. Many fatty acids are unsaturated; some are polyunsaturated (e.g., those derived from
linoleic acid Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt or ester of this acid. L ...
). Most natural fats contain a complex mixture of individual triglycerides. Because of this, they melt over a broad range of temperatures. Cocoa butter is unusual in that it is composed of only a few triglycerides, derived from palmitic, oleic, and
stearic acid Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "''stéar''", which means tall ...
s in the 1-, 2-, and 3-positions of glycerol, respectively.


Homo- and heterotriglycerides

The simplest triglycerides are those where the three fatty acids are identical. Their names indicate the fatty acid:
stearin Stearin , or tristearin, or glyceryl tristearate is an odourless, white powder. It is a triglyceride derived from three units of stearic acid. Most triglycerides are derived from at least two and more commonly three different fatty acids. Like o ...
derived from stearic acid,
palmitin Tripalmitin is a triglyceride derived from the fatty acid palmitic acid Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and micr ...
derived from
palmitic acid Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The L ...
, etc. These compounds can be obtained in three crystalline forms ( polymorphs): α, β, and β′, the three forms differing in their melting points. If the first and third fatty acids on the glycerol differ, then the triglyceride is
chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...
.


Conformation

The shape of fat and fatty acid molecules is usually not well-defined. Any two parts of a molecule that are connected by just one single bond are free to rotate about that bond. Thus a fatty acid molecule with ''n'' simple bonds can be deformed in ''n''-1 independent ways (counting also rotation of the terminal
methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ...
). Such rotation cannot happen across a double bond, except by breaking and then reforming it with one of the halves of the molecule rotated by 180 degrees, which requires crossing a significant energy barrier. Thus a fat or fatty acid molecule with double bonds (excluding at the very end of the chain) can have multiple cis–trans isomers with significantly different chemical and biological properties. Each double bond reduces the number of conformational
degrees of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...
by one. Each triple bond forces the four nearest carbons to lie in a straight line, removing two degrees of freedom. It follows that depictions of "saturated" fatty acids with no double bonds (like stearic) having a "straight zig-zag" shape, and those with one ''cis'' bond (like oleic) being bent in an "elbow" shape are somewhat misleading. While the latter are a little less flexible, both can be twisted to assume similar straight or elbow shapes. In fact, outside of some specific contexts like crystals or bilayer membranes, both are more likely to be found in randomly contorted configurations than in either of those two shapes.


Examples

Stearic acid is a saturated fatty acid (with only single bonds) found in animal fats, and is the intended product in full hydrogenation. Oleic acid has a double bond (thus being "unsaturated") with ''cis'' geometry about midway in the chain; it makes up 55–80% of olive oil. Elaidic acid is its ''trans'' isomer; it may be present in partially hydrogenated vegetable oils, and also occurs in the fat of the
durian The durian (, ) is the edible fruit of several tree species belonging to the genus ''Durio''. There are 30 recognised ''Durio'' species, at least nine of which produce edible fruit. ''Durio zibethinus'', native to Borneo and Sumatra, is the onl ...
fruit (about 2%) and in milk fat (less than 0.1%). Vaccenic acid is another ''trans'' acid that differs from elaidic only in the position of the double bond; it also occurs in milk fat (about 1–2%).


Nomenclature


Common fat names

Fats are usually named after their source (like
olive oil Olive oil is a liquid fat obtained from olives (the fruit of ''Olea europaea''; family Oleaceae), a traditional tree crop of the Mediterranean Basin, produced by pressing whole olives and extracting the oil. It is commonly used in cooking: ...
,
cod liver oil Cod liver oil is a dietary supplement derived from liver of cod fish (Gadidae). As with most fish oils, it contains the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and also vitamin A and vitamin D. Histor ...
,
shea butter Shea butter (, , or ; ) is a fat extracted from yellow the nut of the African shea tree (''Vitellaria paradoxa''). It is ivory in color when raw and commonly dyed yellow with borututu root or palm oil. It is widely used in cosmetics as a ...
, tail fat) or have traditional names of their own (like butter, lard,
ghee Ghee is a type of clarified butter, originating from India. It is commonly used in India for cooking, as a traditional medicine, and for religious rituals. Description Ghee is typically prepared by simmering butter, which is churned from ...
, and
margarine Margarine (, also , ) is a spread used for flavoring, baking, and cooking. It is most often used as a substitute for butter. Although originally made from animal fats, most margarine consumed today is made from vegetable oil. The spread was or ...
). Some of these names refer to products that contain substantial amounts of other components besides fats proper.


Chemical fatty acid names

In chemistry and biochemistry, dozens of saturated fatty acids and of hundreds of unsaturated ones have traditional scientific/technical names usually inspired by their source fats (butyric, caprylic, stearic, oleic, palmitic, and nervonic), but sometimes their discoverer (
mead Mead () is an alcoholic beverage made by fermenting honey mixed with water, and sometimes with added ingredients such as fruits, spices, grains, or hops. The alcoholic content ranges from about 3.5% ABV to more than 20%. The defining charact ...
, osbond). A triglyceride would then be named as an ester of those acids, such as "glyceryl 1,2-dioleate 3-palmitate".N. Koeniger and H. J. Veith (1983): "Glyceryl-1,2-dioleate-3-palmitate, a brood pheromone of the honey bee (''Apis mellifera'' L.)". ''Experientia'', volume 39, pages 1051–1052


IUPAC

In the general chemical nomenclature developed by the
International Union of Pure and Applied Chemistry The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
(IUPAC), the recommended name of a fatty acid, derived from the name of the corresponding
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak ...
, completely describes its structure, by specifying the number of carbons and the number and position of the double bonds. Thus, for example, oleic acid would be called "(9Z)-octadec-9-enoic acid", meaning that it has an 18 carbon chain ("octadec") with a carboxyl at one end ("oic") and a double bond at carbon 9 counting from the carboxyl ("9-en"), and that the configuration of the single bonds adjacent to that double bond is ''cis'' ("(9Z)") The IUPAC nomenclature can also handle branched chains and derivatives where hydrogen atoms are replaced by other chemical groups. A triglyceride would then be named according to general ester rules as, for example, "propane-1,2,3-tryl 1,2-bis((9Z)-octadec-9-enoate) 3-(hexadecanoate)".


Fatty acid code

A notation specific for fatty acids with unbranched chain, that is as precise as the IUPAC one but easier to parse, is a code of the form ": cis- trans-", where is the number of carbons (including the carboxyl one), is the number of double bonds, is a list of the positions of the ''cis'' double bonds, and is a list of the positions of the ''trans'' bonds. Either list and the label is omitted if there are no bonds of that type. Thus, for example, the codes for stearic, oleic, elaidic, and vaccenic acids would be "18:0", "18:1 cis-9", "18:1 trans-9", and "18:1 trans-11", respectively. The code for α-oleostearic acid, which is "(9E,11E,13Z)-octadeca-9,11,13-trienoic acid" in the IUPAC nomenclature, has the code "18:3 trans-9,11 cis-13"


Classification


By chain length

Fats can be classified according to the lengths of the carbon chains of their constituent fatty acids. Most chemical properties, such as melting point and acidity, vary gradually with this parameter, so there is no sharp division. Chemically,
formic acid Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Es ...
(1 carbon) and
acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
(2 carbons) could be viewed as the shortest fatty acids; then triformin would be the simplest triglyceride. However, the terms "fatty acid" and "fat" are usually reserved for compounds with substantially longer chains. A division commonly made in biochemistry and nutrition is: * Short-chain fatty acid (SCFA) with fewer than six carbons (e. g. butyric acid). * Medium-chain fatty acid (MCFA) with 6 to 12 carbons (e.g.
capric acid Capric acid, also known as decanoic acid or decylic acid, is a saturated fatty acid, medium-chain fatty acid (MCFA), and carboxylic acid. Its formula is CH3(CH2)8COOH. Salts and esters of decanoic acid are called caprates or decanoates. The ter ...
). * Long-chain fatty acids (LCFA) with 13 to 21 carbons (e.g.
petroselinic acid Petroselinic acid is a fatty acid that occurs naturally in several animal and vegetable fats and oils. It is a white powder and is commercially available. In chemical terms, petroselinic acid is classified as a monounsaturated omega-12 fatty a ...
). * Very long chain fatty acids (VLCFA) with 22 or more carbons (e. g. cerotic acid with 26) A triglyceride molecule may have fatty acid elements of different lengths, and a fat product will often be a mix of various triglycerides. Most fats found in food, whether vegetable or animal, are made up of medium to long-chain fatty acids, usually of equal or nearly equal length.


Saturated and unsaturated fats

For human nutrition, an important classification of fats is based on the number and position of
double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist bet ...
s in the constituent fatty acids. Saturated fat has a predominance of saturated fatty acids, without any double bonds, while unsaturated fat has predominantly unsaturated acids with double bonds. (The names refer to the fact that each double bond means two fewer hydrogen atoms in the chemical formula. Thus, a saturated fatty acid, having no double bonds, has the maximum number of hydrogen atoms for a given number of carbon atomsthat is, it is "saturated" with hydrogen atoms.) Unsaturated fatty acids are further classified into
monounsaturated In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food. The term often refers specifically to triglycerides (triple est ...
(MUFAs), with a single double bond, and
polyunsaturated In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food. The term often refers specifically to triglycerides (triple est ...
(PUFAs), with two or more. Natural fats usually contain several different saturated and unsaturated acids, even on the same molecule. For example, in most vegetable oils, the saturated palmitic (C16:0) and stearic (C18:0) acid residues are usually attached to positions 1 and 3 (sn1 and sn3) of the glycerol hub, whereas the middle position (sn2) is usually occupied by an unsaturated one, such as oleic (C18:1, ω–9) or linoleic (C18:2, ω–6).) While it is the ''nutritional'' aspects of polyunsaturated fatty acids that are generally of greatest interest, these materials also have non-food applications. They include the
drying oil A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air, at room temperature. The oil hardens through a chemical reaction in which the components crosslink (and hence, polymerize) by the action of oxygen (not ...
s, such as linseed (flax seed), tung, poppyseed,
perilla ''Perilla'' is a genus consisting of one major Asiatic crop species ''Perilla frutescens'' and a few wild species in nature belonging to the mint family, Lamiaceae. The genus encompasses several distinct varieties of Asian herb, seed, and vege ...
, and
walnut oil Walnut oil is oil extracted from walnuts, '' Juglans regia''. The oil contains polyunsaturated fatty acids, monounsaturated fatty acids, and saturated fats. Composition Walnut oil is composed largely of polyunsaturated fatty acids (72% of tota ...
, which
polymerize In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many for ...
on exposure to
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well ...
to form solid films, and are used to make
paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in man ...
s and
varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in vario ...
es. Saturated fats generally have a higher melting point than unsaturated ones with the same molecular weight, and thus are more likely to be solid at room temperature. For example, the animal fats
tallow Tallow is a rendered form of beef or mutton fat, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain technical criteria, includi ...
and
lard Lard is a semi-solid white fat product obtained by rendering the fatty tissue of a pig.Lard
entry in the ...
are high in saturated fatty acid content and are solids. Olive and linseed oils on the other hand are unsaturated and liquid. Unsaturated fats are prone to
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
by air, which causes them to become rancid and inedible. The double bonds in unsaturated fats can be converted into single bonds by reaction with hydrogen effected by a catalyst. This process, called
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic c ...
, is used to turn vegetable oils into solid or semisolid vegetable fats like
margarine Margarine (, also , ) is a spread used for flavoring, baking, and cooking. It is most often used as a substitute for butter. Although originally made from animal fats, most margarine consumed today is made from vegetable oil. The spread was or ...
, which can substitute for tallow and butter and (unlike unsaturated fats) can be stored indefinitely without becoming rancid. However, partial hydrogenation also creates some unwanted ''trans'' acids from ''cis'' acids. In cellular
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...
, unsaturated fat molecules yield slightly less energy (i.e., fewer calories) than an equivalent amount of saturated fat. The heats of combustion of saturated, mono-, di-, and tri-unsaturated 18-carbon fatty acid esters have been measured as 2859, 2828, 2794, and 2750 kcal/mol, respectively; or, on a weight basis, 10.75, 10.71, 10.66, and 10.58 kcal/ga decrease of about 0.6% for each additional double bond. The greater the degree of unsaturation in a fatty acid (i.e., the more double bonds in the fatty acid) the more vulnerable it is to
lipid peroxidation Lipid peroxidation is the chain of reactions of oxidative degradation of lipids. It is the process in which free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by a free radical chai ...
( rancidity).
Antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricants, ...
s can protect unsaturated fat from lipid peroxidation.


Cis and trans fats

Another important classification of unsaturated fatty acids considers the ''cis''–''trans'' isomerism, the spatial arrangement of the C–C
single bond In chemistry, a single bond is a chemical bond between two atoms involving two valence electrons. That is, the atoms share one pair of electrons where the bond forms. Therefore, a single bond is a type of covalent bond. When shared, each of ...
s adjacent to the double bonds. Most unsaturated fatty acids that occur in nature have those bonds in the ''cis'' ("same side") configuration. Partial hydrogenation of ''cis'' fats can turn some of their fatty acids into ''trans'' ("opposite sides") variety.
Elaidic acid Elaidic acid is a chemical compound with the formula , specifically the fatty acid with structural formula HO(O=)C–(CH2–)7CH=CH–(CH2–)8H, with the double bond (between carbon atoms 9 and 10) in ''trans'' configuration. It is a colorless ...
is the ''trans'' isomer of oleic acid, one of the most common fatty acids in human diet. The single change of configuration in one double bond causes them to have different chemical and physical properties. Elaidic acid has a much higher melting point than oleic acid, 45 °C instead of 13.4 °C. This difference is commonly attributed to the supposed ability of the trans molecules to pack more tightly, forming a solid that is more difficult to break apart.


Omega number

Another classification considers the position of the double bonds relative to the ''end'' of the chain (opposite to the carboxyl group). The position is denoted by "ω−''k''" or "n−''k''", meaning that there is a double bond between carbons ''k'' and ''k''+1 counted from 1 at that end. For example,
alpha-Linolenic acid ''alpha''-Linolenic acid (ALA), also known as α-Linolenic acid (from Greek ''alpha'' meaning "first" and ''linon'' meaning flax), is an ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, waln ...
is a "ω−3" or "n−3" acid, meaning that there is a double bond between the third and fourth carbons, counted from that end; that is, its
structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bond ...
ends with –CH=CH––.Karen Dooley (2008):
Omega-three fatty acids and diabetes
. Online article at th
University of Florida's UFHealt
website. Accessed on 2020-08-30.


Examples of saturated fatty acids

Some common examples of fatty acids: * Butyric acid with 4 carbon atoms (contained in butter) *
Lauric acid Lauric acid, systematically dodecanoic acid, is a saturated fatty acid with a 12-carbon atom chain, thus having many properties of medium-chain fatty acids. It is a bright white, powdery solid with a faint odor of bay oil or soap. The salts and e ...
with 12 carbon atoms (contained in
coconut oil frameless , right , alt = A cracked coconut and a bottle of coconut oil Coconut oil (or coconut butter) is an edible oil derived from the wick, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat; in warmer climates du ...
,
palm kernel oil Palm kernel oil is an edible plant oil derived from the kernel of the oil palm tree ''Elaeis guineensis''. It is related to other two edible oils: ''palm oil'', extracted from the fruit pulp of the oil palm, and ''coconut oil'', extracted from ...
, and
breast milk Breast milk (sometimes spelled as breastmilk) or mother's milk is milk produced by mammary glands located in the breast of a human female. Breast milk is the primary source of nutrition for newborns, containing fat, protein, carbohydrates ( lact ...
) * Myristic acid with 14 carbon atoms (contained in cow's
milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modul ...
and dairy products) *
Palmitic acid Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The L ...
with 16 carbon atoms (contained in
palm oil Palm oil is an edible vegetable oil derived from the mesocarp (reddish pulp) of the fruit of the oil palms. The oil is used in food manufacturing, in beauty products, and as biofuel. Palm oil accounted for about 33% of global oils produced fro ...
and
meat Meat is animal flesh that is eaten as food. Humans have hunted, farmed, and scavenged animals for meat since prehistoric times. The establishment of settlements in the Neolithic Revolution allowed the domestication of animals such as c ...
) *
Stearic acid Stearic acid ( , ) is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "''stéar''", which means tall ...
with 18 carbon atoms (also contained in
meat Meat is animal flesh that is eaten as food. Humans have hunted, farmed, and scavenged animals for meat since prehistoric times. The establishment of settlements in the Neolithic Revolution allowed the domestication of animals such as c ...
and
cocoa butter Cocoa butter, also called theobroma oil, is a pale-yellow, edible fat extracted from the cocoa bean. It is used to make chocolate, as well as some ointments, toiletries, and pharmaceuticals. Cocoa butter has a cocoa flavor and aroma. Its melt ...
)


Examples of unsaturated fatty acids

* Myristoleic acid C14:1, ω−5, ''cis''-9-tetradecenoic acid *
Sapienic acid Sapienic acid is a fatty acid that is a major component of human sebum. Sapienic acid is a sebum fatty acid that is unique to humans (from whose scientific name it takes the root ''sapiens''). The equivalent fatty acid in mouse sebum is palmitole ...
C16:1 ω−10, ''cis''-6-Hexadecenoic acid *
Palmitoleic acid Palmitoleic acid, or (9''Z'')-hexadec-9-enoic acid, is an omega-7 monounsaturated fatty acid (16:1n-7) with the formula CH3(CH2)5CH=CH(CH2)7COOH that is a common constituent of the glycerides of human adipose tissue. It is present in all tissu ...
C16:1, ω−7 , ''cis''-9-hexadecenoic acid *
Oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...
C18:1 ω−9, ''cis''-9-octadecenoic acid *
Petroselinic acid Petroselinic acid is a fatty acid that occurs naturally in several animal and vegetable fats and oils. It is a white powder and is commercially available. In chemical terms, petroselinic acid is classified as a monounsaturated omega-12 fatty a ...
C18:1 ω−12, ''cis''-Octadec-6-enoic acid * ''cis''-Vaccenic acid, C18:1 ω−7), ''cis''-11-octadecenoic acid *
Vaccenic acid Vaccenic acid is a naturally occurring trans fatty acid. It is the predominant kind of trans-fatty acid found in human milk, in the fat of ruminants, and in dairy products such as milk, butter, and yogurt. Trans fat in human milk may depend on t ...
C18:1 ω−7, ''trans''-11-octadecenoic acid *
Elaidic acid Elaidic acid is a chemical compound with the formula , specifically the fatty acid with structural formula HO(O=)C–(CH2–)7CH=CH–(CH2–)8H, with the double bond (between carbon atoms 9 and 10) in ''trans'' configuration. It is a colorless ...
18:1 ω−9, ''trans''-9-octadecenoic acid (''trans''-oleic acid) *
Linoleic acid Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt or ester of this acid. L ...
*
Linolenic acid Linolenic acid is a type of naturally-occurring fatty acid. It can refer to either of two octadecatrienoic acids (i.e. with an 18-carbon chain and three double bonds, which are found in the '' cis'' configuration), or a mixture of the two. Lino ...
*
Paullinic acid Paullinic acid is an omega-7 fatty acid find in a variety of plant sources, including guarana (''Paullinia cupana'') from which it gets its name. It is one of a number of eicosenoic acids. See also * 11-Eicosenoic acid References {{Fatty ...
C20:1 ω−7, ''cis''-13-eicosenoic acid * Gadoleic acid C20:1 ω−11, ''cis''-9-icosenoic acid * Gondoic acid 20:1 ω−9, ''cis''-11-eicosenoic acid *
Erucic acid Erucic acid is a monounsaturated omega-9 fatty acid, denoted 22:1ω9. It has the chemical formula CH3(CH2)7CH=CH(CH2)11COOH. It is prevalent in wallflower seed and other plants in the family Brassicaceae, with a reported content of 20 to 54% in ...
C22:1 ω−9, ''cis''-15-docosenoic acid * Brassidic acid C22:1 ω−9, ''trans''-15-docosenoic acid *
Nervonic acid Nervonic acid (24:1, n−9) is a fatty acid. It is a monounsaturated analog of lignoceric acid (24:0). It is also known as selacholeic acid and ''cis''-15-tetracosenoic acid. Its name derives from the Latin word ''nervus'', meaning nerve or si ...
C24:1 ω−9, , ''cis''-15-tetracosenoic acid * Arachidonic acid


Industrial uses

Linseed oil and related oils are important components of useful products used in
oil paint Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnis ...
s and related coatings. Linseed oil is rich in di- and tri-unsaturated fatty acid components, which tend to harden in the presence of oxygen. This heat-producing hardening process is peculiar to these so-called ''drying oils''. It is caused by a
polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many for ...
process that begins with oxygen molecules attacking the carbon backbone. Triglycerides are also split into their components via
transesterification In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction can ...
during the manufacture of
biodiesel Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil wit ...
. The resulting fatty acid esters can be used as fuel in
diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-cal ...
s. The
glycerin Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
has many uses, such as in the manufacture of food and in the production of pharmaceuticals.


Staining

Staining Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the ...
for fatty acids, triglycerides, lipoproteins, and other lipids is done through the use of
lysochrome A lysochrome is a soluble dye used for histochemical staining of lipids, which include triglycerides, fatty acids, and lipoprotein A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid (also known as f ...
s (fat-soluble dyes). These dyes can allow the qualification of a certain fat of interest by staining the material a specific color. Some examples:
Sudan IV Sudan IV (C24H20N4O) is a lysochrome (fat-soluble dye) diazo dye used for the staining of lipids, triglycerides and lipoproteins on frozen paraffin sections. It has the appearance of reddish brown crystals with melting point 199 °C and maxim ...
, Oil Red O, and Sudan Black B.


Interactive pathway map


See also

* Diglyceride acyltransferase, enzyme responsible for triglyceride biosynthesis * Medium-chain triglycerides * Lipid profile *
Lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
s * Vertical auto profile


References


External links


Lowering Triglycerides
(EMedicineHealth.com; October 2020) {{Authority control Lipid disorders Esters