133-508: Lipids are a broad group of organic compounds which include fats , waxes , sterols , fat-soluble vitamins (such as vitamins A , D , E and K ), monoglycerides , diglycerides , phospholipids , and others. The functions of lipids include storing energy, signaling , and acting as structural components of cell membranes . Lipids have applications in the cosmetic and food industries , and in nanotechnology . Lipids may be broadly defined as hydrophobic or amphiphilic small molecules;
266-425: A values of around 16–19, alcohols are, in general, slightly weaker acids than water . With strong bases such as sodium hydride or sodium they form salts called alkoxides , with the general formula RO M (where R is an alkyl and M is a metal ). The acidity of alcohols is strongly affected by solvation . In the gas phase, alcohols are more acidic than in water. In DMSO , alcohols (and water) have
399-416: A ketone ), the glycerol component of triglycerides can be converted into glucose , via gluconeogenesis by conversion into dihydroxyacetone phosphate and then into glyceraldehyde 3-phosphate , for brain fuel when it is broken down. Fat cells may also be broken down for that reason if the brain's needs ever outweigh the body's. Triglycerides cannot pass through cell membranes freely. Special enzymes on
532-533: A century, chemists regarded "fats" as only simple lipids made of fatty acids and glycerol (glycerides), but new forms were described later. Theodore Gobley (1847) discovered phospholipids in mammalian brain and hen egg, called by him as " lecithins ". Thudichum discovered in human brain some phospholipids ( cephalin ), glycolipids ( cerebroside ) and sphingolipids ( sphingomyelin ). The terms lipoid, lipin, lipide and lipid have been used with varied meanings from author to author. In 1912, Rosenbloom and Gies proposed
665-407: A complicated family of compounds that share a common structural feature, a sphingoid base backbone that is synthesized de novo from the amino acid serine and a long-chain fatty acyl CoA, then converted into ceramides , phosphosphingolipids, glycosphingolipids and other compounds. The major sphingoid base of mammals is commonly referred to as sphingosine . Ceramides (N-acyl-sphingoid bases) are
798-414: A cycle of reactions that add the acetyl group, reduce it to an alcohol, dehydrate it to an alkene group and then reduce it again to an alkane group. The enzymes of fatty acid biosynthesis are divided into two groups, in animals and fungi all these fatty acid synthase reactions are carried out by a single multifunctional protein, while in plant plastids and bacteria separate enzymes perform each step in
931-422: A decreased risk of certain cancers, including breast and colorectal cancer, while other studies found no associations with cancer risk. Polyunsaturated fat supplementation was found to have no effect on the incidence of pregnancy-related disorders, such as hypertension or preeclampsia , but may increase the length of gestation slightly and decreased the incidence of early premature births. Expert panels in
1064-416: A diverse family of molecules composed of one or more sugar residues linked via a glycosidic bond to the sphingoid base. Examples of these are the simple and complex glycosphingolipids such as cerebrosides and gangliosides . Sterols, such as cholesterol and its derivatives, are an important component of membrane lipids, along with the glycerophospholipids and sphingomyelins. Other examples of sterols are
1197-422: A dynamic lipid-bilayer matrix as revealed by magnetic resonance and electron microscope studies. A biological membrane is a form of lamellar phase lipid bilayer . The formation of lipid bilayers is an energetically preferred process when the glycerophospholipids described above are in an aqueous environment. This is known as the hydrophobic effect . In an aqueous system, the polar heads of lipids align towards
1330-643: A fatty acid contains a double bond, there is the possibility of either a cis or trans geometric isomerism , which significantly affects the molecule's configuration . Cis -double bonds cause the fatty acid chain to bend, an effect that is compounded with more double bonds in the chain. Three double bonds in 18-carbon linolenic acid , the most abundant fatty-acyl chains of plant thylakoid membranes , render these membranes highly fluid despite environmental low-temperatures, and also makes linolenic acid give dominating sharp peaks in high resolution 13-C NMR spectra of chloroplasts. This in turn plays an important role in
1463-662: A few essential fatty acids that must be included in the diet. Dietary fats are also the carriers of some flavor and aroma ingredients and vitamins that are not water-soluble . In humans and many animals, fats serve both as energy sources and as stores for energy in excess of what the body needs immediately. Each gram of fat when burned or metabolized releases about nine food calories (37 kJ = 8.8 kcal ). Fats are also sources of essential fatty acids , an important dietary requirement. Vitamins A , D , E , and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats play
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#17327724629301596-465: A glycerol core linked to two fatty acid-derived "tails" by ester linkages and to one "head" group by a phosphate ester linkage. While glycerophospholipids are the major component of biological membranes, other non-glyceride lipid components such as sphingomyelin and sterols (mainly cholesterol in animal cell membranes) are also found in biological membranes. In plants and algae, the galactosyldiacylglycerols, and sulfoquinovosyldiacylglycerol, which lack
1729-507: A higher proportion of unsaturated acids, although there are exceptions such as coconut oil and palm kernel oil . Foods containing unsaturated fats include avocado , nuts , olive oils , and vegetable oils such as canola . Many scientific studies have found that replacing saturated fats with cis unsaturated fats in the diet reduces risk of cardiovascular diseases (CVDs), diabetes , or death. These studies prompted many medical organizations and public health departments, including
1862-513: A large fraction of the population in developing countries. Concerns were also expressed at a 2010 conference of the American Dietetic Association that a blanket recommendation to avoid saturated fats could drive people to also reduce the amount of polyunsaturated fats, which may have health benefits, and/or replace fats by refined carbohydrates — which carry a high risk of obesity and heart disease. For these reasons,
1995-458: A linear alcohol: Such processes give fatty alcohols , which are useful for detergents. Some low molecular weight alcohols of industrial importance are produced by the addition of water to alkenes. Ethanol, isopropanol, 2-butanol, and tert -butanol are produced by this general method. Two implementations are employed, the direct and indirect methods. The direct method avoids the formation of stable intermediates, typically using acid catalysts. In
2128-452: A major subclass of sphingoid base derivatives with an amide -linked fatty acid. The fatty acids are typically saturated or mono-unsaturated with chain lengths from 16 to 26 carbon atoms. The major phosphosphingolipids of mammals are sphingomyelins (ceramide phosphocholines), whereas insects contain mainly ceramide phosphoethanolamines and fungi have phytoceramide phosphoinositols and mannose -containing headgroups. The glycosphingolipids are
2261-606: A p K a of around 29–32. As a consequence, alkoxides (and hydroxide) are powerful bases and nucleophiles (e.g., for the Williamson ether synthesis ) in this solvent. In particular, RO or HO in DMSO can be used to generate significant equilibrium concentrations of acetylide ions through the deprotonation of alkynes (see Favorskii reaction ). Tertiary alcohols react with hydrochloric acid to produce tertiary alkyl chloride . Primary and secondary alcohols are converted to
2394-468: A phosphate group, are important components of membranes of chloroplasts and related organelles and are among the most abundant lipids in photosynthetic tissues, including those of higher plants, algae and certain bacteria. Plant thylakoid membranes have the largest lipid component of a non-bilayer forming monogalactosyl diglyceride (MGDG), and little phospholipids; despite this unique lipid composition, chloroplast thylakoid membranes have been shown to contain
2527-535: A primary component of cellular membranes and binding sites for intra- and intercellular proteins, some glycerophospholipids in eukaryotic cells, such as phosphatidylinositols and phosphatidic acids are either precursors of or, themselves, membrane-derived second messengers . Typically, one or both of these hydroxyl groups are acylated with long-chain fatty acids, but there are also alkyl-linked and 1Z-alkenyl-linked ( plasmalogen ) glycerophospholipids, as well as dialkylether variants in archaebacteria. Sphingolipids are
2660-632: A process called fatty acid synthesis . They are made of a hydrocarbon chain that terminates with a carboxylic acid group; this arrangement confers the molecule with a polar , hydrophilic end, and a nonpolar, hydrophobic end that is insoluble in water. The fatty acid structure is one of the most fundamental categories of biological lipids and is commonly used as a building-block of more structurally complex lipids. The carbon chain, typically between four and 24 carbons long, may be saturated or unsaturated , and may be attached to functional groups containing oxygen , halogens , nitrogen , and sulfur . If
2793-405: A process called lipolysis . They are subsequently moved to absorptive enterocyte cells lining the intestines. The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with cholesterol and proteins to form chylomicrons . These are excreted from the cells and collected by the lymph system and transported to the large vessels near the heart before being mixed into
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#17327724629302926-419: A quinonoid core of non-isoprenoid origin. Vitamin E and vitamin K , as well as the ubiquinones , are examples of this class. Prokaryotes synthesize polyprenols (called bactoprenols ) in which the terminal isoprenoid unit attached to oxygen remains unsaturated, whereas in animal polyprenols ( dolichols ) the terminal isoprenoid is reduced. Saccharolipids describe compounds in which fatty acids are linked to
3059-533: A risk factor for cardiovascular disease . Fats that are good for one may be turned into trans fats by improper cooking methods that result in overcooking the lipids. A few studies have suggested that total dietary fat intake is linked to an increased risk of obesity. and diabetes; Others, including the Women's Health Initiative Dietary Modification Trial, an eight-year study of 49,000 women, the Nurses' Health Study, and
3192-423: A significant relationship between saturated fat and high serum cholesterol levels, which in turn have been claimed to have a causal relation with increased risk of cardiovascular disease (the so-called lipid hypothesis ). However, high cholesterol may be caused by many factors. Other indicators, such as high LDL/HDL ratio, have proved to be more predictive. In a study of myocardial infarction in 52 countries,
3325-690: A sugar backbone, forming structures that are compatible with membrane bilayers. In the saccharolipids, a monosaccharide substitutes for the glycerol backbone present in glycerolipids and glycerophospholipids. The most familiar saccharolipids are the acylated glucosamine precursors of the Lipid ;A component of the lipopolysaccharides in Gram-negative bacteria . Typical lipid A molecules are disaccharides of glucosamine, which are derivatized with as many as seven fatty-acyl chains. The minimal lipopolysaccharide required for growth in E. coli
3458-503: A vital role in maintaining healthy skin and hair , insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. Fat also serves as a useful buffer against a host of diseases. When a particular substance, whether chemical or biotic, reaches unsafe levels in the bloodstream, the body can effectively dilute—or at least maintain equilibrium of—the offending substances by storing it in new fat tissue. This helps to protect vital organs, until such time as
3591-466: A water molecule H 2 O . Other less common types of fats include diglycerides and monoglycerides , where the esterification is limited to two or just one of glycerol's –OH groups. Other alcohols, such as cetyl alcohol (predominant in spermaceti ), may replace glycerol. In the phospholipids , one of the fatty acids is replaced by phosphoric acid or a monoester thereof. The benefits and risks of various amounts and types of dietary fats have been
3724-434: A water-cooled still, by which an alcohol purity of 90% could be obtained. The medicinal properties of ethanol were studied by Arnald of Villanova (1240–1311 CE) and John of Rupescissa ( c. 1310 –1366), the latter of whom regarded it as a life-preserving substance able to prevent all diseases (the aqua vitae or "water of life", also called by John the quintessence of wine). The word "alcohol" derives from
3857-551: A weak atherogenic effect. Different saturated fatty acids have differing effects on various lipid levels. The evidence for a relation between saturated fat intake and cancer is significantly weaker, and there does not seem to be a clear medical consensus about it. Various animal studies have indicated that the intake of saturated fat has a negative effect on the mineral density of bones . One study suggested that men may be particularly vulnerable. Studies have shown that substituting monounsaturated fatty acids for saturated ones
3990-404: Is steroid biosynthesis . Here, the isoprene units are joined together to make squalene and then folded up and formed into a set of rings to make lanosterol . Lanosterol can then be converted into other steroids such as cholesterol and ergosterol. Beta oxidation is the metabolic process by which fatty acids are broken down in the mitochondria or in peroxisomes to generate acetyl-CoA . For
4123-922: Is Kdo 2 -Lipid A, a hexa-acylated disaccharide of glucosamine that is glycosylated with two 3-deoxy-D-manno-octulosonic acid (Kdo) residues. Polyketides are synthesized by polymerization of acetyl and propionyl subunits by classic enzymes as well as iterative and multimodular enzymes that share mechanistic features with the fatty acid synthases . They comprise many secondary metabolites and natural products from animal, plant, bacterial, fungal and marine sources, and have great structural diversity. Many polyketides are cyclic molecules whose backbones are often further modified by glycosylation , methylation , hydroxylation , oxidation , or other processes. Many commonly used antimicrobial , antiparasitic , and anticancer agents are polyketides or polyketide derivatives, such as erythromycins , tetracyclines , avermectins , and antitumor epothilones . Eukaryotic cells feature
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4256-451: Is a triglyceride , an ester of the triple alcohol glycerol H(–CHOH–) 3 H and three fatty acids. The molecule of a triglyceride can be described as resulting from a condensation reaction (specifically, esterification ) between each of glycerol's –OH groups and the HO– part of the carboxyl group HO(O=)C− of each fatty acid, forming an ester bridge −O−(O=)C− with elimination of
4389-462: Is a type of organic compound that carries at least one hydroxyl ( −OH ) functional group bound to a saturated carbon atom. Alcohols range from the simple, like methanol and ethanol , to complex, like sugars and cholesterol . The presence of an OH group strongly modifies the properties of hydrocarbons, conferring hydrophilic (water-loving) properties. The OH group provides a site at which many reactions can occur. The flammable nature of
4522-457: Is a vital part of the cell signaling . Lipid signaling may occur via activation of G protein-coupled or nuclear receptors , and members of several different lipid categories have been identified as signaling molecules and cellular messengers . These include sphingosine-1-phosphate , a sphingolipid derived from ceramide that is a potent messenger molecule involved in regulating calcium mobilization, cell growth, and apoptosis; diacylglycerol and
4655-741: Is about 75% monounsaturated fat. The high oleic variety sunflower oil contains at least 70% monounsaturated fat. Canola oil and cashews are both about 58% monounsaturated fat. Tallow (beef fat) is about 50% monounsaturated fat, and lard is about 40% monounsaturated fat. Other sources include hazelnut , avocado oil , macadamia nut oil , grapeseed oil , groundnut oil ( peanut oil ), sesame oil , corn oil , popcorn , whole grain wheat , cereal , oatmeal , almond oil , hemp oil , and tea-oil camellia . Polyunsaturated fatty acids can be found mostly in nuts, seeds, fish, seed oils, and oysters . Food sources of polyunsaturated fats include: MUFAs (especially oleic acid) have been found to lower
4788-417: Is also important in biological systems, particularly with respect to sight. Other major lipid classes in the fatty acid category are the fatty esters and fatty amides. Fatty esters include important biochemical intermediates such as wax esters , fatty acid thioester coenzyme A derivatives, fatty acid thioester ACP derivatives and fatty acid carnitines. The fatty amides include N-acyl ethanolamines , such as
4921-520: Is always pronounced (ɪd). In 1947, T. P. Hilditch defined "simple lipids" as greases and waxes (true waxes, sterols, alcohols). Lipids have been classified into eight categories by the Lipid MAPS consortium as follows: Fatty acyls, a generic term for describing fatty acids, their conjugates and derivatives, are a diverse group of molecules synthesized by chain-elongation of an acetyl-CoA primer with malonyl-CoA or methylmalonyl-CoA groups in
5054-400: Is an alcohol. However, some compounds that contain hydroxyl functional groups have trivial names that do not include the suffix -ol or the prefix hydroxy- , e.g. the sugars glucose and sucrose . IUPAC nomenclature is used in scientific publications, and in writings where precise identification of the substance is important. In naming simple alcohols, the name of the alkane chain loses
5187-413: Is an area of study within biophysics . Micelles and bilayers form in the polar medium by a process known as the hydrophobic effect. When dissolving a lipophilic or amphiphilic substance in a polar environment, the polar molecules (i.e., water in an aqueous solution) become more ordered around the dissolved lipophilic substance, since the polar molecules cannot form hydrogen bonds to the lipophilic areas of
5320-413: Is an oversupply of dietary carbohydrate, the excess carbohydrate is converted to triglycerides. This involves the synthesis of fatty acids from acetyl-CoA and the esterification of fatty acids in the production of triglycerides, a process called lipogenesis . Fatty acids are made by fatty acid synthases that polymerize and then reduce acetyl-CoA units. The acyl chains in the fatty acids are extended by
5453-459: Is associated with increased daily physical activity and resting energy expenditure. More physical activity, less anger, and less irritability were associated with a higher-oleic acid diet than one of a palmitic acid diet. The most common fatty acids in human diet are unsaturated or mono-unsaturated. Monounsaturated fats are found in animal flesh such as red meat , whole milk products, nuts, and high fat fruits such as olives and avocados. Olive oil
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5586-477: Is beneficial for health. Consuming trans fats has been shown to increase the risk of coronary artery disease in part by raising levels of low-density lipoprotein (LDL, often termed "bad cholesterol"), lowering levels of high-density lipoprotein (HDL, often termed "good cholesterol"), increasing triglycerides in the bloodstream and promoting systemic inflammation. Alcohols In chemistry , an alcohol (from Arabic al-kuḥl 'the kohl '),
5719-607: Is contrary to the suggestion that polyunsaturated fats are shown to be protective against insulin resistance. The large scale KANWU study found that increasing MUFA and decreasing SFA intake could improve insulin sensitivity, but only when the overall fat intake of the diet was low. However, some MUFAs may promote insulin resistance (like the SFAs), whereas PUFAs may protect against it. Levels of oleic acid along with other MUFAs in red blood cell membranes were positively associated with breast cancer risk. The saturation index (SI) of
5852-408: Is formed. Tertiary alcohols are eliminated easily at just above room temperature, but primary alcohols require a higher temperature. This is a diagram of acid catalyzed dehydration of ethanol to produce ethylene : [REDACTED] A more controlled elimination reaction requires the formation of the xanthate ester . Tertiary alcohols react with strong acids to generate carbocations. The reaction
5985-436: Is in the form of triglycerides, cholesterol, and phospholipids. Some dietary fat is necessary to facilitate absorption of fat-soluble vitamins ( A , D , E , and K ) and carotenoids . Humans and other mammals have a dietary requirement for certain essential fatty acids, such as linoleic acid (an omega-6 fatty acid ) and alpha-linolenic acid (an omega-3 fatty acid) because they cannot be synthesized from simple precursors in
6118-468: Is less acutely toxic. All alcohols are mild skin irritants. Methanol and ethylene glycol are more toxic than other simple alcohols. Their metabolism is affected by the presence of ethanol, which has a higher affinity for liver alcohol dehydrogenase . In this way, methanol will be excreted intact in urine. In general, the hydroxyl group makes alcohols polar . Those groups can form hydrogen bonds to one another and to most other compounds. Owing to
6251-521: Is partially modulated by dietary fat ratios ( omega−3 / 6 / 9 ) with both omega−3 and −9 thought to be anti-inflammatory, and omega−6 pro-inflammatory (as well as by numerous other dietary components, particularly polyphenols and exercise, with both of these anti-inflammatory). Although both pro- and anti-inflammatory types of fat are biologically necessary, fat dietary ratios in most US diets are skewed towards omega−6, with subsequent disinhibition of inflammation and potentiation of insulin resistance. This
6384-415: Is related to their dehydration, e.g. isobutylene from tert -butyl alcohol. A special kind of dehydration reaction involves triphenylmethanol and especially its amine-substituted derivatives. When treated with acid, these alcohols lose water to give stable carbocations, which are commercial dyes. Alcohol and carboxylic acids react in the so-called Fischer esterification . The reaction usually requires
6517-581: Is the asymmetric reduction of β-keto-esters. Alkenes engage in an acid catalyzed hydration reaction using concentrated sulfuric acid as a catalyst that gives usually secondary or tertiary alcohols. Formation of a secondary alcohol via alkene reduction and hydration is shown: The hydroboration-oxidation and oxymercuration-reduction of alkenes are more reliable in organic synthesis. Alkenes react with N -bromosuccinimide and water in halohydrin formation reaction . Amines can be converted to diazonium salts , which are then hydrolyzed. With aqueous p K
6650-508: Is the focus on this article, the following are most important industrial alcohols: Methanol is the most common industrial alcohol, with about 12 million tons/y produced in 1980. The combined capacity of the other alcohols is about the same, distributed roughly equally. With respect to acute toxicity, simple alcohols have low acute toxicities . Doses of several milliliters are tolerated. For pentanols , hexanols , octanols , and longer alcohols, LD50 range from 2–5 g/kg (rats, oral). Ethanol
6783-508: The ApoB / ApoA1 (related to LDL and HDL, respectively) ratio was the strongest predictor of CVD among all risk factors. There are other pathways involving obesity , triglyceride levels, insulin sensitivity , endothelial function , and thrombogenicity , among others, that play a role in CVD, although it seems, in the absence of an adverse blood lipid profile, the other known risk factors have only
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#17327724629306916-470: The International Union of Pure and Applied Chemistry (IUPAC) chemical name of all substances where the hydroxyl group is the functional group with the highest priority. When a higher priority group is present in the compound, the prefix hydroxy- is used in its IUPAC name. The suffix -ol in non-IUPAC names (such as paracetamol or cholesterol ) also typically indicates that the substance
7049-468: The Mediterranean Sea area, includes more total fat than the diet of Northern European countries, but most of it is in the form of unsaturated fatty acids (specifically, monounsaturated and omega-3) from olive oil and fish, vegetables, and certain meats like lamb, while consumption of saturated fat is minimal in comparison. A 2017 review found evidence that a Mediterranean-style diet could reduce
7182-480: The World Health Organization (WHO), to officially issue that advice. Some countries with such recommendations include: A 2004 review concluded that "no lower safe limit of specific saturated fatty acid intakes has been identified" and recommended that the influence of varying saturated fatty acid intakes against a background of different individual lifestyles and genetic backgrounds should be
7315-481: The Ziegler process , linear alcohols are produced from ethylene and triethylaluminium followed by oxidation and hydrolysis. An idealized synthesis of 1-octanol is shown: The process generates a range of alcohols that are separated by distillation . Many higher alcohols are produced by hydroformylation of alkenes followed by hydrogenation. When applied to a terminal alkene , as is common, one typically obtains
7448-415: The bile acids and their conjugates, which in mammals are oxidized derivatives of cholesterol and are synthesized in the liver. The plant equivalents are the phytosterols , such as β-sitosterol , stigmasterol , and brassicasterol ; the latter compound is also used as a biomarker for algal growth. The predominant sterol in fungal cell membranes is ergosterol . Sterols are steroids in which one of
7581-468: The cannabinoid neurotransmitter anandamide . Glycerolipids are composed of mono-, di-, and tri-substituted glycerols , the best-known being the fatty acid triesters of glycerol, called triglycerides . The word "triacylglycerol" is sometimes used synonymously with "triglyceride". In these compounds, the three hydroxyl groups of glycerol are each esterified, typically by different fatty acids. Because they function as an energy store, these lipids comprise
7714-504: The carotenoids , are made by the assembly and modification of isoprene units donated from the reactive precursors isopentenyl pyrophosphate and dimethylallyl pyrophosphate . These precursors can be made in different ways. In animals and archaea , the mevalonate pathway produces these compounds from acetyl-CoA, while in plants and bacteria the non-mevalonate pathway uses pyruvate and glyceraldehyde 3-phosphate as substrates. One important reaction that uses these activated isoprene donors
7847-407: The circulation . These metabolic activities are regulated by several hormones (e.g., insulin , glucagon and epinephrine ). Adipose tissue also secretes the hormone leptin . A variety of chemical and physical techniques are used for the production and processing of fats, both industrially and in cottage or home settings. They include: The pancreatic lipase acts at the ester bond, hydrolyzing
7980-401: The citric acid cycle and the electron transport chain . Hence the citric acid cycle can start at acetyl-CoA when fat is being broken down for energy if there is little or no glucose available. The energy yield of the complete oxidation of the fatty acid palmitate is 106 ATP. Unsaturated and odd-chain fatty acids require additional enzymatic steps for degradation. Most of the fat found in food
8113-545: The phosphatidylinositol phosphates (PIPs), involved in calcium-mediated activation of protein kinase C ; the prostaglandins , which are one type of fatty-acid derived eicosanoid involved in inflammation and immunity ; the steroid hormones such as estrogen , testosterone and cortisol , which modulate a host of functions such as reproduction, metabolism and blood pressure; and the oxysterols such as 25-hydroxy-cholesterol that are liver X receptor agonists . Phosphatidylserine lipids are known to be involved in signaling for
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#17327724629308246-476: The progestogens as well as the glucocorticoids and mineralocorticoids . The secosteroids , comprising various forms of vitamin D , are characterized by cleavage of the B ring of the core structure. Prenol lipids are synthesized from the five-carbon-unit precursors isopentenyl diphosphate and dimethylallyl diphosphate , which are produced mainly via the mevalonic acid (MVA) pathway. The simple isoprenoids (linear alcohols, diphosphates, etc.) are formed by
8379-744: The rumen of these animals. CLA has two double bonds, one in the cis configuration and one in trans , which makes it simultaneously a cis - and a trans -fatty acid. Concerns about trans fatty acids in human diet were raised when they were found to be an unintentional byproduct of the partial hydrogenation of vegetable and fish oils. While these trans fatty acids (popularly called "trans fats") are edible, they have been implicated in many health problems. The hydrogenation process, invented and patented by Wilhelm Normann in 1902, made it possible to turn relatively cheap liquid fats such as whale or fish oil into more solid fats and to extend their shelf-life by preventing rancidification. (The source fat and
8512-458: The 18th century and was extended to the class of substances so-called as "alcohols" in modern chemistry after 1850. The term ethanol was invented in 1892, blending " ethane " with the "-ol" ending of "alcohol", which was generalized as a libfix . The term alcohol originally referred to the primary alcohol ethanol (ethyl alcohol), which is used as a drug and is the main alcohol present in alcoholic drinks . The suffix -ol appears in
8645-863: The AHA estimated that replacement of saturated fat with polyunsaturated fat in the American diet could reduce the risk of cardiovascular diseases by 30%. The consumption of saturated fat is generally considered a risk factor for dyslipidemia —abnormal blood lipid levels, including high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol). These parameters in turn are believed to be risk indicators for some types of cardiovascular disease. These effects were observed in children too. Several meta-analyses (reviews and consolidations of multiple previously published experimental studies) have confirmed
8778-677: The Arabic kohl ( Arabic : الكحل , romanized : al-kuḥl ), a powder used as an eyeliner. The first part of the word ( al- ) is the Arabic definite article , equivalent to the in English. The second part of the word ( kuḥl ) has several antecedents in Semitic languages , ultimately deriving from the Akkadian 𒎎𒋆𒁉𒍣𒁕 ( guḫlum ), meaning stibnite or antimony . Like its antecedents in Arabic and older languages,
8911-558: The Health Professionals Follow-up Study, revealed no such links. None of these studies suggested any connection between percentage of calories from fat and risk of cancer, heart disease, or weight gain. The Nutrition Source, a website maintained by the department of nutrition at the T. H. Chan School of Public Health at Harvard University , summarizes the current evidence on the effect of dietary fat: "Detailed research—much of it done at Harvard—shows that
9044-582: The U.S. Food and Drug Administration , for example, recommends to consume at least 10% (7% for high-risk groups) of calories from saturated fat, with an average of 30% (or less) of total calories from all fat. A general 7% limit was recommended also by the American Heart Association (AHA) in 2006. The WHO/FAO report also recommended replacing fats so as to reduce the content of myristic and palmitic acids, specifically. The so-called Mediterranean diet , prevalent in many countries in
9177-726: The United States and Europe recommend that pregnant and lactating women consume higher amounts of polyunsaturated fats than the general population to enhance the DHA status of the fetus and newborn. In nature, unsaturated fatty acids generally have double bonds in cis configuration (with the adjacent C–C bonds on the same side) as opposed to trans . Nevertheless, trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep), typically 2–5% of total fat. Natural TFAs, which include conjugated linoleic acid (CLA) and vaccenic acid , originate in
9310-566: The amphiphile. So in an aqueous environment, the water molecules form an ordered " clathrate " cage around the dissolved lipophilic molecule. The formation of lipids into protocell membranes represents a key step in models of abiogenesis , the origin of life. Triglycerides, stored in adipose tissue, are a major form of energy storage both in animals and plants. They are a major source of energy in aerobic respiration. The complete oxidation of fatty acids releases about 38 kJ/g (9 kcal/g ), compared with only 17 kJ/g (4 kcal/g) for
9443-641: The amphiphilic nature of some lipids allows them to form structures such as vesicles , multilamellar/ unilamellar liposomes , or membranes in an aqueous environment. Biological lipids originate entirely or in part from two distinct types of biochemical subunits or "building-blocks": ketoacyl and isoprene groups. Using this approach, lipids may be divided into eight categories: fatty acyls , glycerolipids , glycerophospholipids , sphingolipids , saccharolipids , and polyketides (derived from condensation of ketoacyl subunits); and sterol lipids and prenol lipids (derived from condensation of isoprene subunits). Although
9576-436: The blood. Various tissues can capture the chylomicrons, releasing the triglycerides to be used as a source of energy. Liver cells can synthesize and store triglycerides. When the body requires fatty acids as an energy source, the hormone glucagon signals the breakdown of the triglycerides by hormone-sensitive lipase to release free fatty acids. As the brain cannot utilize fatty acids as an energy source (unless converted to
9709-406: The bond and "releasing" the fatty acid. In triglyceride form, lipids cannot be absorbed by the duodenum . Fatty acids, monoglycerides (one glycerol, one fatty acid), and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down. In the intestine , following the secretion of lipases and bile , triglycerides are split into monoacylglycerol and free fatty acids in
9842-642: The brain) contains relatively high amounts of glycerophospholipids, and alterations in their composition has been implicated in various neurological disorders. Glycerophospholipids may be subdivided into distinct classes, based on the nature of the polar headgroup at the sn -3 position of the glycerol backbone in eukaryotes and eubacteria, or the sn -1 position in the case of archaebacteria . Examples of glycerophospholipids found in biological membranes are phosphatidylcholine (also known as PC, GPCho or lecithin ), phosphatidylethanolamine (PE or GPEtn) and phosphatidylserine (PS or GPSer). In addition to serving as
9975-448: The bulk of storage fat in animal tissues. The hydrolysis of the ester bonds of triglycerides and the release of glycerol and fatty acids from adipose tissue are the initial steps in metabolizing fat. Additional subclasses of glycerolipids are represented by glycosylglycerols, which are characterized by the presence of one or more sugar residues attached to glycerol via a glycosidic linkage . Examples of structures in this category are
10108-483: The cells or cell fragments exposing them. The "fat-soluble" vitamins ( A , D , E and K ) – which are isoprene -based lipids – are essential nutrients stored in the liver and fatty tissues, with a diverse range of functions. Acyl-carnitines are involved in the transport and metabolism of fatty acids in and out of mitochondria, where they undergo beta oxidation . Polyprenols and their phosphorylated derivatives also play important transport roles, in this case
10241-512: The compartmentalized membrane-bound organelles that carry out different biological functions. The glycerophospholipids are the main structural component of biological membranes , as the cellular plasma membrane and the intracellular membranes of organelles; in animal cells, the plasma membrane physically separates the intracellular components from the extracellular environment. The glycerophospholipids are amphipathic molecules (containing both hydrophobic and hydrophilic regions) that contain
10374-500: The concept not only the traditional fats (glycerides), but also the "lipoids", with a complex constitution. The word lipide was unanimously approved by the international commission of the Société de Chimie Biologique during the plenary session on July 3, 1923. The word lipide was later anglicized as lipid because of its pronunciation ('lɪpɪd). In French, the suffix -ide , from Ancient Greek -ίδης (meaning 'son of' or 'descendant of'),
10507-489: The corresponding chlorides using thionyl chloride and various phosphorus chloride reagents. [REDACTED] Primary and secondary alcohols, likewise, convert to alkyl bromides using phosphorus tribromide , for example: In the Barton-McCombie deoxygenation an alcohol is deoxygenated to an alkane with tributyltin hydride or a trimethylborane -water complex in a radical substitution reaction. Meanwhile,
10640-482: The diet. In 1815, Henri Braconnot classified lipids ( graisses ) in two categories, suifs (solid greases or tallow) and huiles (fluid oils). In 1823, Michel Eugène Chevreul developed a more detailed classification, including oils, greases, tallow, waxes, resins, balsams and volatile oils (or essential oils). The first synthetic triglyceride was reported by Théophile-Jules Pelouze in 1844, when he produced tributyrin by treating butyric acid with glycerin in
10773-421: The diet. Both of these fatty acids are 18-carbon polyunsaturated fatty acids differing in the number and position of the double bonds. Most vegetable oils are rich in linoleic acid ( safflower , sunflower , and corn oils). Alpha-linolenic acid is found in the green leaves of plants and in some seeds, nuts, and legumes (in particular flax , rapeseed , walnut , and soy ). Fish oils are particularly rich in
10906-399: The digalactosyldiacylglycerols found in plant membranes and seminolipid from mammalian sperm cells . Glycerophospholipids, usually referred to as phospholipids (though sphingomyelins are also classified as phospholipids), are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and cell signaling . Neural tissue (including
11039-653: The elimination (alkene) product instead. Grignard reagents react with carbonyl groups to give secondary and tertiary alcohols. Related reactions are the Barbier reaction and the Nozaki-Hiyama reaction . Aldehydes or ketones are reduced with sodium borohydride or lithium aluminium hydride (after an acidic workup). Another reduction using aluminium isopropoxide is the Meerwein-Ponndorf-Verley reduction . Noyori asymmetric hydrogenation
11172-474: The exhalations of wine was already known to ancient natural philosophers such as Aristotle (384–322 BCE), Theophrastus ( c. 371 –287 BCE), and Pliny the Elder (23/24–79 CE). However, this did not immediately lead to the isolation of alcohol, even despite the development of more advanced distillation techniques in second- and third-century Roman Egypt . An important recognition, first found in one of
11305-490: The focus in future studies. This advice is often oversimplified by labeling the two kinds of fats as bad fats and good fats , respectively. However, since the fats and oils in most natural and traditionally processed foods contain both unsaturated and saturated fatty acids, the complete exclusion of saturated fat is unrealistic and possibly unwise. For instance, some foods rich in saturated fat, such as coconut and palm oil, are an important source of cheap dietary calories for
11438-437: The form RR'CHOH, the simplest of which is 2-propanol ( R = R' = CH 3 ). For the tertiary alcohols, the general form is RR'R"COH. The simplest example is tert -butanol (2-methylpropan-2-ol), for which each of R, R', and R" is CH 3 . In these shorthands, R, R', and R" represent substituents , alkyl or other attached, generally organic groups. Alcohols have a long history of myriad uses. For simple mono-alcohols, which
11571-791: The hydrocarbon hexane , and 34.6 °C for diethyl ether . Alcohols occur widely in nature, as derivatives of glucose such as cellulose and hemicellulose , and in phenols and their derivatives such as lignin . Starting from biomass , 180 billion tons/y of complex carbohydrates (sugar polymers) are produced commercially (as of 2014). Many other alcohols are pervasive in organisms, as manifested in other sugars such as fructose and sucrose , in polyols such as glycerol , and in some amino acids such as serine . Simple alcohols like methanol, ethanol, and propanol occur in modest quantities in nature, and are industrially synthesized in large quantities for use as chemical precursors, fuels, and solvents. Many alcohols are produced by hydroxylation , i.e.,
11704-483: The hydrogen atoms is substituted with a hydroxyl group , at position 3 in the carbon chain. They have in common with steroids the same fused four-ring core structure. Steroids have different biological roles as hormones and signaling molecules . The eighteen-carbon (C18) steroids include the estrogen family whereas the C19 steroids comprise the androgens such as testosterone and androsterone . The C21 subclass includes
11837-536: The hydroxyl group is bonded to the end or middle carbon on the straight propane chain. As described under systematic naming, if another group on the molecule takes priority, the alcohol moiety is often indicated using the "hydroxy-" prefix. In archaic nomenclature, alcohols can be named as derivatives of methanol using "-carbinol" as the ending. For instance, (CH 3 ) 3 COH can be named trimethylcarbinol . Alcohols are then classified into primary, secondary ( sec- , s- ), and tertiary ( tert- , t- ), based upon
11970-408: The incidence of insulin resistance ; PUFAs (especially large amounts of arachidonic acid ) and SFAs (such as arachidic acid ) increased it. These ratios can be indexed in the phospholipids of human skeletal muscle and in other tissues as well. This relationship between dietary fats and insulin resistance is presumed secondary to the relationship between insulin resistance and inflammation , which
12103-432: The indirect method, the alkene is converted to the sulfate ester , which is subsequently hydrolyzed. The direct hydration uses ethylene ( ethylene hydration ) or other alkenes from cracking of fractions of distilled crude oil . Hydration is also used industrially to produce the diol ethylene glycol from ethylene oxide . Ethanol is obtained by fermentation of glucose (which is often obtained from starch ) in
12236-478: The inner mitochondrial membrane. They are believed to activate enzymes involved with oxidative phosphorylation . Lipids also form the basis of steroid hormones. The major dietary lipids for humans and other animals are animal and plant triglycerides, sterols, and membrane phospholipids. The process of lipid metabolism synthesizes and degrades the lipid stores and produces the structural and functional lipids characteristic of individual tissues. In animals, when there
12369-431: The installation of a hydroxy group using oxygen or a related oxidant. Hydroxylation is the means by which the body processes many poisons , converting lipophilic compounds into hydrophilic derivatives that are more readily excreted. Enzymes called hydroxylases and oxidases facilitate these conversions. Many industrial alcohols, such as cyclohexanol for the production of nylon , are produced by hydroxylation. In
12502-497: The longer-chain omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid . Many studies have shown positive health benefits associated with consumption of omega-3 fatty acids on infant development, cancer, cardiovascular diseases, and various mental illnesses (such as depression, attention-deficit hyperactivity disorder, and dementia). In contrast, it is now well-established that consumption of trans fats , such as those present in partially hydrogenated vegetable oils , are
12635-424: The main components of vegetable oils and of fatty tissue in animals; or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thus excluding oils . The term may also be used more broadly as a synonym of lipid —any substance of biological relevance, composed of carbon , hydrogen , or oxygen , that is insoluble in water but soluble in non-polar solvents . In this sense, besides
12768-419: The main components of common food products like milk , butter , tallow , lard , salt pork , and cooking oils . They are a major and dense source of food energy for many animals and play important structural and metabolic functions in most living beings, including energy storage, waterproofing, and thermal insulation . The human body can produce the fat it requires from other food ingredients, except for
12901-504: The merits of substituting polyunsaturated fats for saturated fats. The effect of saturated fat on cardiovascular disease has been extensively studied. The general consensus is that there is evidence of moderate-quality of a strong, consistent, and graded relationship between saturated fat intake, blood cholesterol levels, and the incidence of cardiovascular disease. The relationships are accepted as causal, including by many government and medical organizations. A 2017 review by
13034-500: The molecule is classified separately as a phenol and is named using the IUPAC rules for naming phenols. Phenols have distinct properties and are not classified as alcohols. In other less formal contexts, an alcohol is often called with the name of the corresponding alkyl group followed by the word "alcohol", e.g., methyl alcohol, ethyl alcohol. Propyl alcohol may be n -propyl alcohol or isopropyl alcohol , depending on whether
13167-468: The most part, fatty acids are oxidized by a mechanism that is similar to, but not identical with, a reversal of the process of fatty acid synthesis. That is, two-carbon fragments are removed sequentially from the carboxyl end of the acid after steps of dehydrogenation , hydration , and oxidation to form a beta-keto acid , which is split by thiolysis . The acetyl-CoA is then ultimately converted into adenosine triphosphate (ATP), CO 2 , and H 2 O using
13300-430: The number of carbon atoms connected to the carbon atom that bears the hydroxyl functional group . The respective numeric shorthands 1°, 2°, and 3° are sometimes used in informal settings. The primary alcohols have general formulas RCH 2 OH . The simplest primary alcohol is methanol ( CH 3 OH ), for which R = H, and the next is ethanol, for which R = CH 3 , the methyl group . Secondary alcohols are those of
13433-1054: The object of much study, and are still highly controversial topics. There are two essential fatty acids (EFAs) in human nutrition: alpha-Linolenic acid (an omega-3 fatty acid ) and linoleic acid (an omega-6 fatty acid ). The adult body can synthesize other lipids that it needs from these two. Different foods contain different amounts of fat with different proportions of saturated and unsaturated fatty acids. Some animal products, like beef and dairy products made with whole or reduced fat milk like yogurt , ice cream , cheese and butter have mostly saturated fatty acids (and some have significant contents of dietary cholesterol ). Other animal products, like pork , poultry , eggs , and seafood have mostly unsaturated fats. Industrialized baked goods may use fats with high unsaturated fat contents as well, especially those containing partially hydrogenated oils , and processed foods that are deep-fried in hydrogenated oil are high in saturated fat content. Plants and fish oil generally contain
13566-416: The observed health impact of replacing dietary saturated fat with linoleic acid found that it increased rates of death from all causes, coronary heart disease, and cardiovascular disease. These studies have been disputed by many scientists, and the consensus in the medical community is that saturated fat and cardiovascular disease are closely related. Still, these discordant studies fueled debate over
13699-508: The offending substances can be metabolized or removed from the body by such means as excretion , urination , accidental or intentional bloodletting , sebum excretion, and hair growth. In animals, adipose tissue , or fatty tissue is the body's means of storing metabolic energy over extended periods of time. Adipocytes (fat cells) store fat derived from the diet and from liver metabolism . Under energy stress these cells may degrade their stored fat to supply fatty acids and also glycerol to
13832-411: The oxidative breakdown of carbohydrates and proteins . The adipocyte , or fat cell, is designed for continuous synthesis and breakdown of triglycerides in animals, with breakdown controlled mainly by the activation of hormone-sensitive enzyme lipase . Migratory birds that must fly long distances without eating use triglycerides to fuel their flights. Evidence has emerged showing that lipid signaling
13965-464: The oxygen atom has lone pairs of nonbonded electrons that render it weakly basic in the presence of strong acids such as sulfuric acid . For example, with methanol: [REDACTED] Upon treatment with strong acids, alcohols undergo the E1 elimination reaction to produce alkenes . The reaction, in general, obeys Zaitsev's Rule , which states that the most stable (usually the most substituted) alkene
14098-458: The pathway. The fatty acids may be subsequently converted to triglycerides that are packaged in lipoproteins and secreted from the liver. The synthesis of unsaturated fatty acids involves a desaturation reaction, whereby a double bond is introduced into the fatty acyl chain. For example, in humans, the desaturation of stearic acid by stearoyl-CoA desaturase-1 produces oleic acid . The doubly unsaturated fatty acid linoleic acid as well as
14231-585: The pattern was reversed: the Hungarian product containing twice the trans fat of the New York product. Even within the United States, there was variation, with fries in New York containing 30% more trans fat than those from Atlanta . Numerous studies have found that consumption of TFAs increases risk of cardiovascular disease. The Harvard School of Public Health advises that replacing TFAs and saturated fats with cis monounsaturated and polyunsaturated fats
14364-400: The phagocytosis of apoptotic cells or pieces of cells. They accomplish this by being exposed to the extracellular face of the cell membrane after the inactivation of flippases which place them exclusively on the cytosolic side and the activation of scramblases, which scramble the orientation of the phospholipids. After this occurs, other cells recognize the phosphatidylserines and phagocytosize
14497-418: The polar, aqueous environment, while the hydrophobic tails minimize their contact with water and tend to cluster together, forming a vesicle ; depending on the concentration of the lipid, this biophysical interaction may result in the formation of micelles , liposomes , or lipid bilayers . Other aggregations are also observed and form part of the polymorphism of amphiphile (lipid) behavior. Phase behavior
14630-435: The prefix hydroxy- is used, e.g., as in 1-hydroxy-2-propanone ( CH 3 C(O)CH 2 OH ). Compounds having more than one hydroxy group are called polyols . They are named using suffixes -diol, -triol, etc., following a list of the position numbers of the hydroxyl groups, as in propane-1,2-diol for CH 3 CH(OH)CH 2 OH (propylene glycol). In cases where the hydroxy group is bonded to an sp carbon on an aromatic ring ,
14763-534: The presence of concentrated sulfuric acid . Several years later, Marcellin Berthelot , one of Pelouze's students, synthesized tristearin and tripalmitin by reaction of the analogous fatty acids with glycerin in the presence of gaseous hydrogen chloride at high temperature. In 1827, William Prout recognized fat ("oily" alimentary matters), along with protein ("albuminous") and carbohydrate ("saccharine"), as an important nutrient for humans and animals. For
14896-413: The presence of the polar OH alcohols are more water-soluble than simple hydrocarbons. Methanol, ethanol, and propanol are miscible in water. 1-Butanol , with a four-carbon chain, is moderately soluble. Because of hydrogen bonding , alcohols tend to have higher boiling points than comparable hydrocarbons and ethers . The boiling point of the alcohol ethanol is 78.29 °C, compared to 69 °C for
15029-542: The presence of yeast. Carbon dioxide is cogenerated. Like ethanol, butanol can be produced by fermentation processes. Saccharomyces yeast are known to produce these higher alcohols at temperatures above 75 °F (24 °C). The bacterium Clostridium acetobutylicum can feed on cellulose (also an alcohol) to produce butanol on an industrial scale. Primary alkyl halides react with aqueous NaOH or KOH to give alcohols in nucleophilic aliphatic substitution . Secondary and especially tertiary alkyl halides will give
15162-432: The process were initially kept secret to avoid consumer distaste. ) This process was widely adopted by the food industry in the early 1900s; first for the production of margarine , a replacement for butter and shortening, and eventually for various other fats used in snack food, packaged baked goods, and deep fried products. Full hydrogenation of a fat or oil produces a fully saturated fat. However, hydrogenation generally
15295-491: The risk of cardiovascular diseases, overall cancer incidence, neurodegenerative diseases, diabetes, and mortality rate. A 2018 review showed that a Mediterranean-like diet may improve overall health status, such as reduced risk of non-communicable diseases. It also may reduce the social and economic costs of diet-related illnesses. A small number of contemporary reviews have challenged this negative view of saturated fats. For example, an evaluation of evidence from 1966 to 1973 of
15428-532: The same membranes was inversely associated with breast cancer risk. MUFAs and low SI in erythrocyte membranes are predictors of postmenopausal breast cancer. Both of these variables depend on the activity of the enzyme delta-9 desaturase (Δ9-d). Results from observational clinical trials on PUFA intake and cancer have been inconsistent and vary by numerous factors of cancer incidence, including gender and genetic risk. Some studies have shown associations between higher intakes and/or blood levels of omega-3 PUFAs and
15561-445: The structure and function of cell membranes. Most naturally occurring fatty acids are of the cis configuration, although the trans form does exist in some natural and partially hydrogenated fats and oils. Examples of biologically important fatty acids include the eicosanoids , derived primarily from arachidonic acid and eicosapentaenoic acid , that include prostaglandins , leukotrienes , and thromboxanes . Docosahexaenoic acid
15694-477: The substitution of "lipoid" by "lipin". In 1920, Bloor introduced a new classification for "lipoids": simple lipoids (greases and waxes), compound lipoids (phospholipoids and glycolipoids), and the derived lipoids (fatty acids, alcohols , sterols). The word lipide , which stems etymologically from Greek λίπος, lipos 'fat', was introduced in 1923 by the French pharmacologist Gabriel Bertrand . Bertrand included in
15827-436: The successive addition of C5 units, and are classified according to number of these terpene units. Structures containing greater than 40 carbons are known as polyterpenes. Carotenoids are important simple isoprenoids that function as antioxidants and as precursors of vitamin A . Another biologically important class of molecules is exemplified by the quinones and hydroquinones , which contain an isoprenoid tail attached to
15960-428: The term alcohol was originally used for the very fine powder produced by the sublimation of the natural mineral stibnite to form antimony trisulfide Sb 2 S 3 . It was considered to be the essence or "spirit" of this mineral. It was used as an antiseptic , eyeliner, and cosmetic . Later the meaning of alcohol was extended to distilled substances in general, and then narrowed again to ethanol, when "spirits"
16093-506: The term "lipid" is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides . Lipids also encompass molecules such as fatty acids and their derivatives (including tri-, di-, monoglycerides, and phospholipids), as well as other sterol -containing metabolites such as cholesterol . Although humans and other mammals use various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids cannot be made this way and must be obtained from
16226-413: The terminal e and adds the suffix -ol , e.g. , as in "ethanol" from the alkane chain name " ethane ". When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the -ol : propan-1-ol for CH 3 CH 2 CH 2 OH , propan-2-ol for CH 3 CH(OH)CH 3 . If a higher priority group is present (such as an aldehyde , ketone , or carboxylic acid ), then
16359-443: The total amount of fat in the diet isn't really linked with weight or disease." Introductory Nomenclature Databases General Fat 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 esters of glycerol ), that are
16492-963: The total fat in those foods containing man-made trans fats formed by partially hydrogenating plant fats may be trans fat. Baking shortenings, unless reformulated, contain around 30% trans fats compared to their total fats. High-fat dairy products such as butter contain about 4%. Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight, but some reformulated ones are less than 1% trans fat. High levels of TFAs have been recorded in popular "fast food" meals. An analysis of samples of McDonald's French fries collected in 2004 and 2005 found that fries served in New York City contained twice as much trans fat as in Hungary , and 28 times as much as in Denmark , where trans fats are restricted. For Kentucky Fried Chicken products,
16625-509: The transport of oligosaccharides across membranes. Polyprenol phosphate sugars and polyprenol diphosphate sugars function in extra-cytoplasmic glycosylation reactions, in extracellular polysaccharide biosynthesis (for instance, peptidoglycan polymerization in bacteria), and in eukaryotic protein N- glycosylation . Cardiolipins are a subclass of glycerophospholipids containing four acyl chains and three glycerol groups that are particularly abundant in
16758-415: The triglycerides, the term would include several other types of compounds like mono- and diglycerides , phospholipids (such as lecithin ), sterols (such as cholesterol ), waxes (such as beeswax ), and free fatty acids, which are usually present in human diet in smaller amounts. Fats are one of the three main macronutrient groups in human diet , along with carbohydrates and proteins , and
16891-418: The triply unsaturated α-linolenic acid cannot be synthesized in mammalian tissues, and are therefore essential fatty acids and must be obtained from the diet. Triglyceride synthesis takes place in the endoplasmic reticulum by metabolic pathways in which acyl groups in fatty acyl-CoAs are transferred to the hydroxyl groups of glycerol-3-phosphate and diacylglycerol. Terpenes and isoprenoids , including
17024-430: The twelfth century, recipes for the production of aqua ardens ("burning water", i.e., alcohol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century, it had become a widely known substance among Western European chemists. The works of Taddeo Alderotti (1223–1296) describe a method for concentrating alcohol involving repeated fractional distillation through
17157-632: The walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Fatty acids can then be taken up by cells via fatty acid transport proteins (FATPs). Triglycerides, as major components of very-low-density lipoprotein (VLDL) and chylomicrons , play an important role in metabolism as energy sources and transporters of dietary fat. They contain more than twice as much energy (approximately 9 kcal/g or 38 kJ /g) as carbohydrates (approximately 4 kcal/g or 17 kJ/g). The most common type of fat, in human diet and most living beings,
17290-605: The word as "antimonium sive stibium." By extension, the word came to refer to any fluid obtained by distillation, including "alcohol of wine," the distilled essence of wine. Libavius in Alchymia (1594) refers to " vini alcohol vel vinum alcalisatum ". Johnson (1657) glosses alcohol vini as " quando omnis superfluitas vini a vino separatur, ita ut accensum ardeat donec totum consumatur, nihilque fæcum aut phlegmatis in fundo remaneat ." The word's meaning became restricted to "spirit of wine" (the chemical known today as ethanol ) in
17423-511: The writings attributed to Jābir ibn Ḥayyān (ninth century CE), was that by adding salt to boiling wine, which increases the wine's relative volatility , the flammability of the resulting vapors may be enhanced. The distillation of wine is attested in Arabic works attributed to al-Kindī ( c. 801 –873 CE) and to al-Fārābī ( c. 872 –950), and in the 28th book of al-Zahrāwī 's (Latin: Abulcasis, 936–1013) Kitāb al-Taṣrīf (later translated into Latin as Liber servatoris ). In
17556-622: Was a synonym for hard liquor . Paracelsus and Libavius both used the term alcohol to denote a fine powder, the latter speaking of an alcohol derived from antimony. At the same time Paracelsus uses the word for a volatile liquid; alcool or alcool vini occurs often in his writings. Bartholomew Traheron , in his 1543 translation of John of Vigo , introduces the word as a term used by "barbarous" authors for "fine powder." Vigo wrote: "the barbarous auctours use alcohol, or (as I fynde it sometymes wryten) alcofoll, for moost fine poudre." The 1657 Lexicon Chymicum , by William Johnson glosses
17689-781: Was interrupted before completion, to yield a fat product with specific melting point, hardness, and other properties. Partial hydrogenation turns some of the cis double bonds into trans bonds by an isomerization reaction . The trans configuration is favored because it is the lower energy form. This side reaction accounts for most of the trans fatty acids consumed today, by far. An analysis of some industrialized foods in 2006 found up to 30% "trans fats" in artificial shortening, 10% in breads and cake products, 8% in cookies and crackers, 4% in salty snacks, 7% in cake frostings and sweets, and 26% in margarine and other processed spreads. Another 2010 analysis however found only 0.2% of trans fats in margarine and other processed spreads. Up to 45% of
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