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In
chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. T ...

chemistry
, particularly in
biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and pr ...

biochemistry
, a fatty acid is a
carboxylic acid A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO2H, with substituent, R referring to the alkyl, alkenyl, aryl, or other group. ...
with an
aliphatic In organic chemistry, hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen che ...
chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, from 4 to 28. Fatty acids are a major component of the lipids (up to 70 wt%) in some species such as microalgae but in some other organisms are not found in their standalone form, but instead exist as three main classes of
ester An ester is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemic ...

ester
s:
triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a an ...

triglyceride
s,
phospholipid Phospholipids, also known as phosphatides, are a class of lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) disso ...

phospholipid
s, and
cholesteryl ester Cholesterol oleate, a member of the cholesteryl ester family Cholesteryl ester, a dietary lipid In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, che ...
s. In any of these forms, fatty acids are both important
dietary In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the ...
sources of fuel for animals and important structural components for
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
.


History

The concept of fatty acid (''acide gras'') was introduced in 1813 by
Michel Eugène Chevreul Michel Eugène Chevreul (31 August 1786 – 9 April 1889) was a French chemist whose work influenced several areas in science, medicine, and art. His early work with animal fats revolutionized the manufacture of soap and of candles and led to his ...

Michel Eugène Chevreul
, though he initially used some variant terms: ''graisse acide'' and ''acide huileux'' ("acid fat" and "oily acid").


Types of fatty acids

Fatty acids are classified in many ways: by length, by saturation vs unsaturation, by even vs odd carbon content, and by linear vs branched.


Length of fatty acids

*
Short-chain fatty acidsShort-chain fatty acids (SCFAs) are fatty acid fatty acids have perfectly straight chain structure. Unsaturated ones are typically bent, unless they have a trans configuration. In chemistry Chemistry is the scientific discipline involved w ...
(SCFA) are fatty acids with
aliphatic In organic chemistry, hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen che ...
tails of five or fewer
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
s (e.g.
butyric acid Butyric acid (from grc, βούτῡρον, meaning "butter"), also known under the systematic name butanoic acid, is a straight-chain alkyl In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study o ...

butyric acid
). *
Medium-chain fatty acids Medium-chain triglycerides (MCTs) are triglycerides with two or three fatty acids having an aliphatic compound, aliphatic tail of 6–12 carbon atoms, i.e., medium-chain fatty acids (MCFAs). Rich food sources for commercial extraction of MCTs inclu ...
(MCFA) are fatty acids with aliphatic tails of 6 to 12 carbons, which can form
medium-chain triglyceride Medium-chain triglycerides (MCTs) are triglyceride 300px, Example of an unsaturated fat triglyceride (C55H98O6). Left part: glycerol; right part, from top to bottom: palmitic acid, oleic acid">palmitic_acid.html" ;"title="glycerol; right part, fr ...
s. *
Long-chain fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...
(LCFA) are fatty acids with aliphatic tails of 13 to 21 carbons. *
Very long chain fatty acids A very-long-chain fatty acid (VLCFA) is a fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, pro ...
(VLCFA) are fatty acids with aliphatic tails of 22 or more carbons.


Saturated fatty acids

Saturated fatty acids have no C=C double bonds. They have the same formula CH(CH)COOH, with variations in "n". An important saturated fatty acid is
stearic acid Stearic acid ( , ) is a saturated fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properti ...

stearic acid
(n = 16), which when neutralized with lye is the most common form of
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
.


Unsaturated fatty acids

Unsaturated fatty acids have one or more C=C
double bond In chemistry, a double bond is a covalent bond A covalent bond is a chemical bond A chemical bond is a lasting attraction between atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, ...

double bond
s. The C=C double bonds can give either ''cis'' or ''trans'' isomers. ; ''cis'' :A ''cis'' configuration means that the two hydrogen atoms adjacent to the double bond stick out on the same side of the chain. The rigidity of the double bond freezes its conformation and, in the case of the ''cis'' isomer, causes the chain to bend and restricts the conformational freedom of the fatty acid. The more double bonds the chain has in the ''cis'' configuration, the less flexibility it has. When a chain has many ''cis'' bonds, it becomes quite curved in its most accessible conformations. For example,
oleic acid Oleic acid is a fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and t ...

oleic acid
, with one double bond, has a "kink" in it, whereas
linoleic acid Linoleic acid is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules ...

linoleic acid
, with two double bonds, has a more pronounced bend.
α-Linolenic acid α-Linolenic acid (ALA), (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxi ...

α-Linolenic acid
, with three double bonds, favors a hooked shape. The effect of this is that, in restricted environments, such as when fatty acids are part of a phospholipid in a lipid bilayer or triglycerides in lipid droplets, cis bonds limit the ability of fatty acids to be closely packed, and therefore can affect the melting temperature of the membrane or of the fat. Cis unsaturated fatty acids, however, increase cellular membrane fluidity, whereas trans unsaturated fatty acids do not. ; ''trans'' : A ''trans'' configuration, by contrast, means that the adjacent two hydrogen atoms lie on ''opposite'' sides of the chain. As a result, they do not cause the chain to bend much, and their shape is similar to straight saturated fatty acids. In most naturally occurring unsaturated fatty acids, each double bond has three ( n-3), six ( n-6), or nine ( n-9) carbon atoms after it, and all double bonds have a cis configuration. Most fatty acids in the ''trans'' configuration (
trans fat Trans fat, also called trans-unsaturated fatty acids or trans fatty acids, is a type of that naturally occurs in small amounts in meat and milk fat. It became widely produced as an unintentional byproduct in the industrial processing of vegetable ...
s) are not found in nature and are the result of human processing (e.g.,
hydrogenation Hydrogenation is a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical A chemical substance is a form of matter having constant ...

hydrogenation
). Some trans fatty acids also occur naturally in the milk and meat of
ruminant Ruminants (suborder Ruminantia) are large ungulate, hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, princi ...
s (such as cattle and sheep). They are produced, by fermentation, in the rumen of these animals. They are also found in
dairy product Dairy products or milk products are a type of food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, such a ...
s from milk of ruminants, and may be also found in
breast milk . Breast milk or mother's milk is milk Milk is a nutrient-rich liquid food produced by the mammary gland A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their nam ...
of women who obtained them from their diet. The geometric differences between the various types of unsaturated fatty acids, as well as between saturated and unsaturated fatty acids, play an important role in biological processes, and in the construction of biological structures (such as cell membranes).


Even- vs odd-chained fatty acids

Most fatty acids are even-chained, e.g. stearic (C18) and oleic (C18), meaning they are composed of an even number of carbon atoms. Some fatty acids have odd numbers of carbon atoms; they are referred to as odd-chained fatty acids (OCFA). The most common OCFA are the saturated C15 and C17 derivatives,
pentadecanoic acid Pentadecylic acid, or pentadecanoic acid, is a saturated fatty acid fatty acids have perfectly straight chain structure. Unsaturated compound, Unsaturated ones are typically bent, unless they have a #Unsaturated fatty acids, trans configuration. ...

pentadecanoic acid
and
heptadecanoic acid Margaric acid, or heptadecanoic acid, is a crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are close ...

heptadecanoic acid
respectively, which are found in dairy products. On a molecular level, OCFAs are biosynthesized and metabolized slightly differently from the even-chained relatives.


Nomenclature


Carbon atom numbering

Most naturally occurring fatty acids have an unbranched chain of carbon atoms, with a
carboxyl group A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO2H, with substituent, R referring to the alkyl, alkenyl, aryl, or other group. ...

carboxyl group
(–COOH) at one end, and a
methyl group A methyl group is an alkyl In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: t ...

methyl group
(–CH3) at the other end. The position of the carbon atoms in the backbone of a fatty acid are usually indicated by counting from 1 at the −COOH end. Carbon number ''x'' is often abbreviated C-''x'' (or sometimes C''x''), with ''x'' = 1, 2, 3, etc. This is the numbering scheme recommended by the
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering OrganizationsNational Adhering Organizations in chemistry are the organizations that work as the authoritative power over chemist ...
. Another convention uses letters of the
Greek alphabet The Greek alphabet has been used to write the Greek language since the late ninth or early eighth century BC. It is derived from the earlier Phoenician alphabet, and was the first alphabetic script in history to have distinct letters for vowels ...

Greek alphabet
in sequence, starting with the first carbon ''after'' the carboxyl. Thus carbon α (
alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', modern pronunciation ''álfa'') is the first letter Letter, letters, or literature may refer to: Characters typeface * Letter (alphabet) A letter is a segmental symbol A s ...

alpha
) is C-2, carbon β (
beta Beta (, ; uppercase , lowercase , or cursive Cursive (also known as script, among other names) is any style of penmanship Penmanship is the technique of writing Writing is a medium of human communication that involves the represen ...

beta
) is C-3, and so forth. Although fatty acids can be of diverse lengths, in this second convention the last carbon in the chain is always labelled as ω (
omega Omega (; capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase or capitals (or more formally ''majuscule'') and smaller lowercase (o ...

omega
), which is the last letter in the Greek alphabet. A third numbering convention counts the carbons from that end, using the labels "ω", "ω−1", "ω−2". Alternatively, the label "ω−''x''" is written "n−''x''", where the "n" is meant to represent the number of carbons in the chain.A common mistake is to say that the last carbon is "ω−1".
Another common mistake is to say that the position of a bond in omega-notation is the number of the carbon closest to the END.
For double bonds, these two mistakes happen to compensate each other; so that a "ω−3" fatty acid indeed has the double bond between the 3rd and 4th carbons from the end, counting the methyl as 1.
However, for substitutions and other purposes, they don't: a hydroxyl "at ω−3" is on carbon 15 (4th from the end), not 16. See for example this article.
Note also that the "−" in the omega-notation is a minus sign, and "ω−3" should in principle be read "omega minus three". However, it is very common (especially in non-scientific literature) to write it "ω-3" (with a hyphen/dash) and read it as "omega-three". See for example Karen Dooley (2008)
Omega-three fatty acids and diabetes
In either numbering scheme, the position of a
double bond In chemistry, a double bond is a covalent bond A covalent bond is a chemical bond A chemical bond is a lasting attraction between atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, ...

double bond
in a fatty acid chain is always specified by giving the label of the carbon closest to the carboxyl end. Thus, in an 18 carbon fatty acid, a double bond between C-12 (or ω−6) and C-13 (or ω−5) is said to be "at" position C-12 or ω−6. The IUPAC naming of the acid, such as "octadec-12-enoic acid" (or the more pronounceable variant "12-octadecanoic acid") is always based on the "C" numbering. The notation Δ''x'',''y'',... is traditionally used to specify a fatty acid with double bonds at positions ''x'',''y'',.... (The capital Greek letter "Δ" (
delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, a landform at the mouth of a river * D (NATO phonetic alphabet: "Delta"), the fourth letter of the modern English alphabet * Delta Air Lines, an Ame ...
) corresponds to
Roman Roman or Romans most often refers to: *Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Laz ...

Roman
"D", for Double bond). Thus, for example, the 20-carbon
arachidonic acid Arachidonic acid (AA, sometimes ARA) is a polyunsaturated In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''org ...

arachidonic acid
is Δ5,8,11,14, meaning that it has double bonds between carbons 5 and 6, 8 and 9, 11 and 12, and 14 and 15. In the context of human diet and fat metabolism, unsaturated fatty acids are often classified by the position of the double bond closest to the ω carbon (only), even in the case of multiple double bonds such as the
essential fatty acid Essential fatty acids, or EFAs, are fatty acid fatty acids have perfectly straight chain structure. Unsaturated compound, Unsaturated ones are typically bent, unless they have a #Unsaturated fatty acids, trans configuration. In chemistry, parti ...
s. Thus
linoleic acid Linoleic acid is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules ...

linoleic acid
(18 carbons, Δ9,12), (18-carbon, Δ6,9,12), and arachidonic acid (20-carbon, Δ5,8,11,14) are all classified as "ω−6" fatty acids; meaning that their
formula In , a formula is a concise way of expressing information symbolically, as in a mathematical formula or a . The informal use of the term ''formula'' in science refers to the . The plural of ''formula'' can be either ''formulas'' (from the mos ...
ends with –CH=CH–––––. Fatty acids with an
odd number In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). I ...
of carbon atoms are called
odd-chain fatty acid Odd-chain fatty acids are those fatty acid fatty acids have perfectly straight chain structure. Unsaturated compound, Unsaturated ones are typically bent, unless they have a #Unsaturated fatty acids, trans configuration. In chemistry, particular ...
s, whereas the rest are even-chain fatty acids. The difference is relevant to gluconeogenesis.


Naming of fatty acids

The following table describes the most common systems of naming fatty acids.


Free fatty acids

When circulating in the
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood plasma ...
(plasma fatty acids), not in their
ester An ester is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemic ...

ester
, fatty acids are known as non-esterified fatty acids (NEFAs) or free fatty acids (FFAs). FFAs are always bound to a
transport protein Transport (commonly used in the U.K.), or transportation (used in the U.S.), is the movement of humans, animals and goods In economics Economics () is the social science that studies how people interact with value; in particular, t ...
, such as
albumin Albumin is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subje ...
. FFAs also form from
triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a an ...

triglyceride
food oils and fats by hydrolysis, contributing to the characteristic rancid odor. An analogous process happens in
biodiesel Biodiesel is a form of diesel fuel Diesel fuel in general is any liquid fuel Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy In physical sciences Physical science is a ...

biodiesel
with risk of part corrosion.


Production


Industrial

Fatty acids are usually produced industrially by the
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution Substitution may refer to: Arts and media *Chord substitution, in music, swapping one chord fo ...

hydrolysis
of
triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a an ...

triglyceride
s, with the removal of
glycerol Glycerol (; also called glycerine in British English and glycerin in American English) is a simple polyol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
(see
oleochemical Oleochemistry is the study of vegetable oil Vegetable oils, or vegetable fats, are oil An oil is any nonpolar chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any s ...
s).
Phospholipid Phospholipids, also known as phosphatides, are a class of lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) disso ...

Phospholipid
s represent another source. Some fatty acids are produced synthetically by
hydrocarboxylation Carbonylation refers to reactions that introduce carbon monoxide into organic and inorganic In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, m ...
of alkenes.


Hyper-oxygenated fatty acids

Hyper-oxygenated fatty acids are produced by a specific industrial processes for topical skin creams. The process is based on the introduction or saturation of peroxides into fatty acid esters via the presence of ultraviolet light and gaseous oxygen bubbling under controlled temperatures. Specifically
linolenic acid Linolenic acid is a type of fatty acid fatty acids have perfectly straight chain structure. Unsaturated ones are typically bent, unless they have a trans configuration. In chemistry Chemistry is the scientific discipline involved with Ch ...
s have been shown to play an important role in maintaining the moisture barrier function of the skin (preventing water loss and skin dehydration). A study in Spain reported in the Journal of Wound Care in March 2005 compared a commercial product with a greasy
placebo A placebo ( ) is a substance or treatment which is designed to have no therapeutic value. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures. In general, placebos can af ...

placebo
and that specific product was more effective and also cost-effective. A range of such OTC medical products is now widely available. However, topically applied
olive oil Olive oil is a liquid fat obtained from olive The olive, botanical name ''Olea europaea'', meaning "European olive", is a species In biology, a species is the basic unit of biological classification, classification and a taxonomi ...

olive oil
was not found to be inferior in a " randomised triple-blind controlled non-inferiority" trial conducted in Spain during 2015. Commercial products are likely to be less messy to handle and more washable than either olive oil or
petroleum jelly Petroleum jelly, petrolatum, white petrolatum, soft paraffin, or multi-hydrocarbon, CAS number A CAS Registry Number, also referred to as CASRN or CAS Number, is a unique numerical identifier An identifier is a name that identifies (that is, ...
, both of which if applied topically may stain clothing and bedding.


By animals

In animals, fatty acids are formed from carbohydrates predominantly in the
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...

liver
,
adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the many basic types of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biolo ...

adipose tissue
, and the
mammary glands A mammary gland is an exocrine gland Exocrine glands are glands that secrete substances onto an Epithelium, epithelial surface by way of a Duct (anatomy), duct. Examples of exocrine glands include sweat gland, sweat, salivary, mammary, cerumino ...
during lactation. Carbohydrates are converted into
pyruvate Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R ...

pyruvate
by
glycolysis Glycolysis is the metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of on ...

glycolysis
as the first important step in the conversion of carbohydrates into fatty acids. Pyruvate is then decarboxylated to form
acetyl-CoA Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reaction Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organism In biology, an organism (from ...

acetyl-CoA
in the
mitochondrion A mitochondrion (; ) is a double-membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes ...

mitochondrion
. However, this acetyl CoA needs to be transported into
cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a s ...
where the synthesis of fatty acids occurs. This cannot occur directly. To obtain cytosolic acetyl-CoA,
citrate Citric acid is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

citrate
(produced by the condensation of acetyl-CoA with
oxaloacetate Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemi ...

oxaloacetate
) is removed from the
citric acid cycle The citric acid cycle (CAC) – also known as the TCA cycle (tricarboxylic acid cycle) or the Krebs cycle – is a series of chemical reactions to release stored energy through the redox, oxidation of acetyl-CoA derived from carbohydra ...

citric acid cycle
and carried across the inner mitochondrial membrane into the cytosol. There it is cleaved by
ATP citrate lyase ATP citrate synthase (also ATP citrate lyase (ACLY)) is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate ...
into acetyl-CoA and oxaloacetate. The oxaloacetate is returned to the mitochondrion as
malate Malic acid is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavi ...
. The cytosolic acetyl-CoA is carboxylated by
acetyl CoA carboxylase In organic chemistry, acetyl is a moiety, the acyl An acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group (R- ...
into
malonyl-CoA Malonyl-CoA is a coenzyme A Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme A cofactor is a non-protein Proteins are large biomolecules or macromolecules that are comprised of one or more long chains of amino acid residue (biochemistry), residue ...

malonyl-CoA
, the first committed step in the synthesis of fatty acids. Malonyl-CoA is then involved in a repeating series of reactions that lengthens the growing fatty acid chain by two carbons at a time. Almost all natural fatty acids, therefore, have even numbers of carbon atoms. When synthesis is complete the free fatty acids are nearly always combined with glycerol (three fatty acids to one glycerol molecule) to form
triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a an ...

triglyceride
s, the main storage form of fatty acids, and thus of energy in animals. However, fatty acids are also important components of the
phospholipid Phospholipids, also known as phosphatides, are a class of lipid In and , a lipid is a macro that is soluble in solvents. are typically s used to dissolve other naturally occurring hydrocarbon lipid s that do not (or do not easily) disso ...

phospholipid
s that form the
phospholipid bilayers The lipid bilayer (or phospholipid bilayer) is a thin polar membrane A polarized membrane is a lipid bilayer, lipid membrane that has a positive electrical charge on one side and a negative charge on another side, which produces the resting pot ...
out of which all the membranes of the cell are constructed (the
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
, and the membranes that enclose all the
organelles In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
within the cells, such as the
nucleus ''Nucleus'' (plural nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA ...

nucleus
, the
mitochondria A mitochondrion (; ) is a double-membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes ...

mitochondria
,
endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
, and the
Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that stu ...

Golgi apparatus
). The "uncombined fatty acids" or "free fatty acids" found in the circulation of animals come from the breakdown (or
lipolysis upright=1.8, Example of a triacylglycerol Lipolysis is the metabolic pathway In biochemistry Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry ...
) of stored triglycerides. Because they are insoluble in water, these fatty acids are transported bound to plasma
albumin Albumin is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subje ...
. The levels of "free fatty acids" in the blood are limited by the availability of albumin binding sites. They can be taken up from the blood by all cells that have mitochondria (with the exception of the cells of the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
). Fatty acids can only be broken down in mitochondria, by means of
beta-oxidation 350px, Schematic demonstrating mitochondrial fatty acid beta-oxidation and effects of long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency, long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency, LCHAD deficiency In biochemistry an ...
followed by further combustion in the
citric acid cycle The citric acid cycle (CAC) – also known as the TCA cycle (tricarboxylic acid cycle) or the Krebs cycle – is a series of chemical reactions to release stored energy through the redox, oxidation of acetyl-CoA derived from carbohydra ...

citric acid cycle
to CO and water. Cells in the central nervous system, although they possess mitochondria, cannot take free fatty acids up from the blood, as the blood-brain barrier is impervious to most free fatty acids, excluding
short-chain fatty acidShort-chain fatty acids (SCFAs) are fatty acids with fewer than six carbon atoms. Derived from intestine, intestinal microbe, microbial fermentation of indigestible foods, SCFAs are the main energy source of Gastrointestinal_tract#Mucosa, colonocytes ...
s and medium-chain fatty acids. These cells have to manufacture their own fatty acids from carbohydrates, as described above, in order to produce and maintain the phospholipids of their cell membranes, and those of their organelles.


Variation between animal species

Studies on the
cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membra ...

cell membrane
s of
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s and
reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptile
s discovered that mammalian cell membranes are composed of a higher proportion of polyunsaturated fatty acids (,
omega-3 fatty acid Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acid Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This ...
) than
reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptile
s. Studies on bird fatty acid composition have noted similar proportions to mammals but with 1/3rd less omega-3 fatty acids as compared to
omega-6 Omega-6 fatty acids (also referred to as ω-6 fatty acids or ''n''-6 fatty acids) are a family of that have in common a final carbon-carbon in the position, that is, the sixth bond, counting from the end. Biochemistry (18:2, ''n''−6), ...
for a given body size. This fatty acid composition results in a more fluid cell membrane but also one that is permeable to various ions ( & ), resulting in cell membranes that are more costly to maintain. This maintenance cost has been argued to be one of the key causes for the high metabolic rates and concomitant warm-bloodedness of mammals and birds. However polyunsaturation of cell membranes may also occur in response to chronic cold temperatures as well. In
fish Fish are aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

fish
increasingly cold environments lead to increasingly high cell membrane content of both monounsaturated and polyunsaturated fatty acids, to maintain greater membrane fluidity (and functionality) at the lower
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
s.


Fatty acids in dietary fats

The following table gives the fatty acid,
vitamin E Vitamin E is a group of eight fat solubleLipophilicity (from Greek language, Greek λίπος "fat" and :wikt:φίλος, φίλος "friendly"), refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solven ...

vitamin E
and
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
composition of some common dietary fats.


Reactions of fatty acids

Fatty acids exhibit reactions like other carboxylic acids, i.e. they undergo
esterification An ester is a chemical compound derived from an acid (organic or inorganic) in which at least one –OH hydroxyl group is replaced by an –O– alkyl ( alkoxy) group, as in the substitution reaction of a carboxylic acid and an alcohol. Glycer ...

esterification
and acid-base reactions.


Acidity

Fatty acids do not show a great variation in their acidities, as indicated by their respective p''K''.
Nonanoic acid Pelargonic acid, also called nonanoic acid, is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to ca ...

Nonanoic acid
, for example, has a p''K'' of 4.96, being only slightly weaker than acetic acid (4.76). As the chain length increases, the solubility of the fatty acids in water decreases, so that the longer-chain fatty acids have minimal effect on the of an aqueous solution. Near neutral pH, fatty acids exist at their conjugate bases, i.e. oleate, etc. Solutions of fatty acids in
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), ...

ethanol
can be with
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
solution using
phenolphthalein Phenolphthalein is a chemical compound with the chemical formula, formula carbon, C20hydrogen, H14oxygen, O4 and is often written as "HIn" or "phph" in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For ...

phenolphthalein
as an indicator. This analysis is used to determine the free fatty acid content of fats; i.e., the proportion of the triglycerides that have been
hydrolyze Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile In chemistry, a nucleop ...

hydrolyze
d. Neutralization of fatty acids, one form of
saponification Saponification is a process that involves the conversion of fat, oil, or lipid, into soap and alcohol by the action of aqueous alkali (e.g. Sodium hydroxide, NaOH). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon ...

saponification
(soap-making), is a widely practiced route to
metallic soap A metallic soap is a metallic salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline minera ...
s.


Hydrogenation and hardening

Hydrogenation Hydrogenation is a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical A chemical substance is a form of matter having constant ...

Hydrogenation
of unsaturated fatty acids is widely practiced. Typical conditions involve 2.0–3.0 MPa of H pressure, 150 °C, and nickel supported on silica as a catalyst. This treatment affords saturated fatty acids. The extent of hydrogenation is indicated by the
iodine number Iodine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...
. Hydrogenated fatty acids are less prone toward
rancidification Rancidification is the process of complete or incomplete oxidation or hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution Substitution ma ...
. Since the saturated fatty acids are than the unsaturated precursors, the process is called hardening. Related technology is used to convert vegetable oils into
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 foodstuff was or ...

margarine
. The hydrogenation of triglycerides (vs fatty acids) is advantageous because the carboxylic acids degrade the nickel catalysts, affording nickel soaps. During partial hydrogenation, unsaturated fatty acids can be isomerized from ''cis'' to ''trans'' configuration. More forcing hydrogenation, i.e. using higher pressures of H and higher temperatures, converts fatty acids into
fatty alcohol Fatty alcohols (or long-chain alcohols In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated and unsaturated compounds, saturated carbon atom. The term alcohol origina ...
s. Fatty alcohols are, however, more easily produced from fatty acid
ester An ester is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemic ...

ester
s. In the Varrentrapp reaction certain unsaturated fatty acids are cleaved in molten alkali, a reaction which was, at one point of time, relevant to structure elucidation.


Auto-oxidation and rancidity

Unsaturated fatty acids undergo a chemical change known as
auto-oxidationAutoxidation (sometimes auto-oxidation) refers to redox, oxidations brought about by reactions with oxygen at normal temperatures, without the intervention of flame or electric spark. The term is usually used to describe the degradation of organic co ...
. The process requires oxygen (air) and is accelerated by the presence of trace metals. Vegetable oils resist this process to a small degree because they contain antioxidants, such as
tocopherolTocopherols (; TCP) are a class of organic compounds, organic chemical compounds (more precisely, various Methyl group, methylated phenols), many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dieta ...
. Fats and oils often are treated with
chelating agents Chelation is a type of bonding of ions An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All ...
such as
citric acid Citric acid is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, ...

citric acid
to remove the metal catalysts.


Ozonolysis

Unsaturated fatty acids are susceptible to degradation by ozone. This reaction is practiced in the production of
azelaic acid Azelaic acid (AzA) is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenat ...

azelaic acid
((CH)(COH)) from
oleic acid Oleic acid is a fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and t ...

oleic acid
.


Circulation


Digestion and intake

Short- and
medium-chain fatty acids Medium-chain triglycerides (MCTs) are triglycerides with two or three fatty acids having an aliphatic compound, aliphatic tail of 6–12 carbon atoms, i.e., medium-chain fatty acids (MCFAs). Rich food sources for commercial extraction of MCTs inclu ...
are absorbed directly into the blood via intestine capillaries and travel through the
portal vein The portal vein or hepatic portal vein (HPV) is a blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that ...
just as other absorbed nutrients do. However,
long-chain fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...
are not directly released into the intestinal capillaries. Instead they are absorbed into the fatty walls of the intestine villi and reassemble again into
triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a an ...

triglyceride
s. The triglycerides are coated with
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
and protein (protein coat) into a compound called a
chylomicron Chylomicrons (from the Greek χυλός, chylos, meaning ''juice'' (of plants or animals), and micron, meaning ''small particle''), also known as ultra low-density lipoproteins (ULDL), are lipoprotein, lipoprotein particles that consist of trigl ...

chylomicron
. From within the cell, the chylomicron is released into a
lymphatic Lymph (from Latin, ''lympha'' meaning "water") is the fluid that flows through the lymphatic system The lymphatic system, or lymphoid system, is an in vertebrates that is part of the and the . It is made up of a large network of lymph, s, l ...
capillary called a
lacteal A lacteal is a lymphatic capillary that absorbs dietary fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''o ...
, which merges into larger lymphatic vessels. It is transported via the lymphatic system and the
thoracic duct In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the ''left lymphatic duct'', ''alimentary duct'', ''chyliferous duct'', and ''Van Hoorne's canal''. The other duct is the right ly ...
up to a location near the heart (where the arteries and veins are larger). The thoracic duct empties the chylomicrons into the bloodstream via the left
subclavian vein The subclavian vein is a paired large vein Veins are blood vessels The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an Biological sys ...
. At this point the chylomicrons can transport the triglycerides to tissues where they are stored or metabolized for energy.


Metabolism

Fatty acids are broken down to CO and water by the intra-cellular
mitochondria A mitochondrion (; ) is a double-membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes ...

mitochondria
through
beta oxidation 350px, Schematic demonstrating fatty_acid.html"_;"title="mitochondrial_fatty_acid">mitochondrial_fatty_acid_beta-oxidation_and_effects_of_long-chain_3-hydroxyacyl-coenzyme_A_dehydrogenase_deficiency.html" ;"title="fatty_acid_beta-oxidation.html" ...
and the
citric acid cycle The citric acid cycle (CAC) – also known as the TCA cycle (tricarboxylic acid cycle) or the Krebs cycle – is a series of chemical reactions to release stored energy through the redox, oxidation of acetyl-CoA derived from carbohydra ...

citric acid cycle
. In the final step (
oxidative phosphorylation Oxidative phosphorylation (UK , US ) or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell (biology), c ...

oxidative phosphorylation
), reaction with energy-rich oxygen releases a lot of energy, captured in the form of large quantities of
ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals * American Technical Publishers * ', a Danish pension * Armenia Tree Project * Association for Transpersonal Psychology * ATP architects engineers office * ATP ...

ATP
. Many cell types can use either
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
or fatty acids for this purpose, but fatty acids release more energy per gram because they contain less oxygen and therefore unlock the energy of more O. Fatty acids (provided either by ingestion or by drawing on triglycerides stored in fatty tissues) are distributed to cells to serve as a fuel for muscular contraction and general metabolism.


Essential fatty acids

Fatty acids that are required for good health but cannot be made in sufficient quantity from other substrates, and therefore must be obtained from food, are called essential fatty acids. There are two series of essential fatty acids: one has a double bond three carbon atoms away from the methyl end; the other has a double bond six carbon atoms away from the methyl end. Humans lack the ability to introduce double bonds in fatty acids beyond carbons 9 and 10, as counted from the carboxylic acid side. Two essential fatty acids are
linoleic acid Linoleic acid is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules ...

linoleic acid
(LA) and
alpha-linolenic acid α-Linolenic acid (ALA), (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxi ...

alpha-linolenic acid
(ALA). These fatty acids are widely distributed in plant oils. The human body has a limited ability to convert ALA into the longer-chain
omega-3 fatty acid Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acid Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This ...
s — eicosapentaenoic acid (EPA) and
docosahexaenoic acid Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. In physiological literature, it is given the name 22:6(n-3). It can be synthesized from alpha-linol ...

docosahexaenoic acid
(DHA), which can also be obtained from fish. Omega-3 and
omega-6 Omega-6 fatty acids (also referred to as ω-6 fatty acids or ''n''-6 fatty acids) are a family of that have in common a final carbon-carbon in the position, that is, the sixth bond, counting from the end. Biochemistry (18:2, ''n''−6), ...
fatty acids are
biosyntheticBiosynthesis is a multi-step, enzyme-Catalysis, catalyzed process where substrate (chemistry), substrates are converted into more complex Product (chemistry), products in living organisms. In biosynthesis, simple Chemical compound, compounds are modi ...

biosynthetic
precursors to
endocannabinoids Cannabinoids () are compounds found in Cannabis (drug), cannabis. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (Delta9-THC or Delta8-THC), the primary psychoactive drug, psychoactive compound in cannabis. Cannabidi ...
with
antinociceptiveNociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the Somatosensory system, sensory nervous system's process of encoding noxious stimuli. In nociception, intense chemical (e.g., cayenne powder), mechanical (e.g., cutting, cr ...
,
anxiolytic An anxiolytic (; also antipanic or antianxiety agent) is a medication, or other intervention, that reduces anxiety (mood), anxiety. This effect is in contrast to anxiogenic agents, which increase anxiety. Together these categories of Psychoactiv ...
, and
neurogenic In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sensory information by transmitting action potential, signals to and from different parts of its bo ...

neurogenic
properties.


Distribution

Blood fatty acids adopt distinct forms in different stages in the blood circulation. They are taken in through the intestine in
chylomicron Chylomicrons (from the Greek χυλός, chylos, meaning ''juice'' (of plants or animals), and micron, meaning ''small particle''), also known as ultra low-density lipoproteins (ULDL), are lipoprotein, lipoprotein particles that consist of trigl ...

chylomicron
s, but also exist in
very low density lipoprotein Very-low-density lipoprotein (VLDL), density relative to extracellular water, is a type of lipoprotein 250px, Structure of a chylomicron. ApoA, ApoB, ApoC, ApoE are apolipoproteins; green particles are phospholipids; T is triacylglycerol; C is cho ...
s (VLDL) and
low density lipoprotein Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein which transport all fat molecules around the body in the extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall den ...
s (LDL) after processing in the liver. In addition, when released from
adipocytes Adipocytes, also known as lipocytes and fat cells, are the cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or ...

adipocytes
, fatty acids exist in the blood as
free fatty acids fatty acids have perfectly straight chain structure. Unsaturated ones are typically bent, unless they have a trans configuration. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical co ...
. It is proposed that the blend of fatty acids exuded by mammalian skin, together with
lactic acid Lactic acid is an organic acid An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, conta ...

lactic acid
and
pyruvic acid Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R ...

pyruvic acid
, is distinctive and enables animals with a keen sense of smell to differentiate individuals.


Analysis

The chemical analysis of fatty acids in lipids typically begins with an step that breaks down their original esters (triglycerides, waxes, phospholipids etc) and converts them to methyl esters, which are then separated by gas chromatography. or analyzed by gas chromatography and mid-infrared spectroscopy. Separation of unsaturated isomers is possible by Argentation chromatography, silver ion complemented thin-layer chromatography. Other separation techniques include high-performance liquid chromatography (with short columns packed with silica gel with bonded phenylsulfonic acid groups whose hydrogen atoms have been exchanged for silver ions). The role of silver lies in its ability to form complexes with unsaturated compounds.


Industrial uses

Fatty acids are mainly used in the production of
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
, both for cosmetic purposes and, in the case of
metallic soap A metallic soap is a metallic salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline minera ...
s, as lubricants. Fatty acids are also converted, via their methyl esters, to
fatty alcohol Fatty alcohols (or long-chain alcohols In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated and unsaturated compounds, saturated carbon atom. The term alcohol origina ...
s and fatty amines, which are precursors to surfactants, detergents, and lubricants. Other applications include their use as Emulsion#Emulsifiers, emulsifiers, texturizing agents, wetting agents, Defoamer, anti-foam agents, or stabilizing agents. Esters of fatty acids with simpler alcohols (such as methyl-, ethyl-, n-propyl-, isopropyl- and butyl esters) are used as emollients in cosmetics and other personal care products and as synthetic lubricants. Esters of fatty acids with more complex alcohols, such as sorbitol, ethylene glycol, diethylene glycol, and polyethylene glycol are consumed in food, or used for personal care and water treatment, or used as synthetic lubricants or fluids for metal working.


See also

*Fatty acid synthase *Fatty acid synthesis *Fatty aldehyde *List of saturated fatty acids *List of unsaturated fatty acids *List of carboxylic acids *Vegetable oil


References


External links


Lipid Library''Prostaglandins, Leukotrienes & Essential Fatty Acids'' journal
{{DEFAULTSORT:Fatty Acid Fatty acids, Commodity chemicals E-number additives