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80-446: It is an enzyme that resides in a class of enzymes called phospholipase that hydrolyze phospholipids into fatty acids . There are four classes, separated according to the type of reaction they catalyze. In particular, phospholipase A 1 (PLA 1 ) specifically catalyzes the cleavage at the sn -1 position of phospholipids, forming a fatty acid and a lysophospholipid. PLA 1 's are present in numerous species including humans, and have

160-476: A carbonyl group C=O, which is a divalent group at C atom, which gives rise to 120° C–C–O and O–C–O angles. Unlike amides , carboxylic acid esters are structurally flexible functional groups because rotation about the C–O–C bonds has a low barrier. Their flexibility and low polarity is manifested in their physical properties; they tend to be less rigid (lower melting point) and more volatile (lower boiling point) than

240-413: A chylomicron . From within the cell, the chylomicron is released into a lymphatic capillary called a lacteal , which merges into larger lymphatic vessels. It is transported via the lymphatic system and the thoracic duct 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 . At this point

320-444: A dehydrating agent: The equilibrium constant for such reactions is about 5 for typical esters, e.g., ethyl acetate. The reaction is slow in the absence of a catalyst. Sulfuric acid is a typical catalyst for this reaction. Many other acids are also used such as polymeric sulfonic acids . Since esterification is highly reversible, the yield of the ester can be improved using Le Chatelier's principle : Reagents are known that drive

400-619: A broad array of plastics , plasticizers , resins , and lacquers , and are one of the largest classes of synthetic lubricants on the commercial market. Polyesters are important plastics, with monomers linked by ester moieties . Esters of phosphoric acid form the backbone of DNA molecules. Esters of nitric acid , such as nitroglycerin , are known for their explosive properties. There are compounds in which an acidic hydrogen of acids mentioned in this article are not replaced by an organyl, but by some other group. According to some authors, those compounds are esters as well, especially when

480-430: A catalyst. This treatment affords saturated fatty acids. The extent of hydrogenation is indicated by the iodine number . Hydrogenated fatty acids are less prone toward rancidification . Since the saturated fatty acids are higher melting than the unsaturated precursors, the process is called hardening. Related technology is used to convert vegetable oils into margarine . The hydrogenation of triglycerides (vs fatty acids)

560-527: A cis configuration. Most fatty acids in the trans configuration ( trans fats ) are not found in nature and are the result of human processing (e.g., hydrogenation ). Some trans fatty acids also occur naturally in the milk and meat of ruminants (such as cattle and sheep). They are produced, by fermentation, in the rumen of these animals. They are also found in dairy products from milk of ruminants, and may be also found in breast milk of women who obtained them from their diet. The geometric differences between

640-955: A combination of hyperconjugation and dipole minimization effects. The preference for the Z conformation is influenced by the nature of the substituents and solvent, if present. Lactones with small rings are restricted to the s -trans (i.e. E ) conformation due to their cyclic structure. Esters derived from carboxylic acids and alcohols are more polar than ethers but less polar than alcohols. They participate in hydrogen bonds as hydrogen-bond acceptors, but cannot act as hydrogen-bond donors, unlike their parent alcohols. This ability to participate in hydrogen bonding confers some water-solubility. Because of their lack of hydrogen-bond-donating ability, esters do not self-associate. Consequently, esters are more volatile than carboxylic acids of similar molecular weight. Esters are generally identified by gas chromatography, taking advantage of their volatility. IR spectra for esters feature an intense sharp band in

720-417: A fuel for muscular contraction and general metabolism. 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

800-517: A higher proportion of polyunsaturated fatty acids ( DHA , omega−3 fatty acid ) than reptiles . 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 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 ( H & Na ), resulting in cell membranes that are more costly to maintain. This maintenance cost has been argued to be one of

880-475: A p K a 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 pH of an aqueous solution. Near neutral pH, fatty acids exist at their conjugate bases, i.e. oleate, etc. Solutions of fatty acids in ethanol can be titrated with sodium hydroxide solution using phenolphthalein as an indicator. This analysis

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960-565: A part of metal and metalloid alkoxides , of which many hundreds are known, could be classified as esters of the corresponding acids (e.g. aluminium triethoxide ( Al(OCH 2 CH 3 ) 3 ) could be classified as an ester of aluminic acid which is aluminium hydroxide , tetraethyl orthosilicate ( Si(OCH 2 CH 3 ) 4 ) could be classified as an ester of orthosilicic acid , and titanium ethoxide ( Ti(OCH 2 CH 3 ) 4 ) could be classified as an ester of orthotitanic acid ). Esters derived from carboxylic acids and alcohols contain

1040-462: A short lid and B9 domain that span 7-12 and 12-13 amino acids, respectively. Unlike other phospholipases such as PLA 2 , there is much that is unknown about PLA 1 due to the lack of any efficient way to purify, clone, express, and characterize this enzyme. PLA 1 is currently commercially unavailable because of this. Lysophospholipids can be found as surfactants in food techniques and cosmetics, and can be used in drug delivery. Current research

1120-431: A small degree because they contain antioxidants, such as tocopherol . Fats and oils often are treated with chelating agents such as citric acid to remove the metal catalysts. Unsaturated fatty acids are susceptible to degradation by ozone. This reaction is practiced in the production of azelaic acid ((CH 2 ) 7 (CO 2 H) 2 ) from oleic acid . Short- and medium-chain fatty acids are absorbed directly into

1200-605: A variety of cellular functions that include regulation and facilitation of the production of lysophospholipid mediators, and acting as digestive enzymes. These enzymes are responsible for fast turnover rates of cellular phospholipids. In addition to this, the products of the reaction catalyzed by PLA 1 which are a fatty acid and a lysophospholipid are important in various biological functions such as platelet aggregation and smooth muscle contraction. In addition, lysophospholipids can be found as surfactants in food techniques and cosmetics, and can be used in drug delivery. Since PLA 1

1280-418: Is stearic acid ( n  = 16), which when neutralized with sodium hydroxide is the most common form of soap . Unsaturated fatty acids have one or more C=C double bonds . The C=C double bonds can give either cis or trans isomers. 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

1360-684: Is γ-valerolactone . An uncommon class of esters are the orthoesters . One of them are the esters of orthocarboxylic acids. Those esters have the formula RC(OR′) 3 , where R stands for any group (organic or inorganic) and R ′ stands for organyl group. For example, triethyl orthoformate ( HC(OCH 2 CH 3 ) 3 ) is derived, in terms of its name (but not its synthesis) from esterification of orthoformic acid ( HC(OH) 3 ) with ethanol . Esters can also be derived from inorganic acids. Inorganic acids that exist as tautomers form two or more types of esters. Some inorganic acids that are unstable or elusive form stable esters. In principle,

1440-501: Is a compound derived from an acid (organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group ( −OH ) of that acid is replaced by an organyl group (R ′ ). These compounds contain a distinctive functional group . Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well (e.g. amides ), but not according to

1520-542: Is a dibutylstannylene ester of lauric acid , and the Phillips catalyst CrO 2 (OSi(OCH 3 ) 3 ) 2 is a trimethoxysilyl ester of chromic acid ( H 2 CrO 4 ). The word ester was coined in 1848 by a German chemist Leopold Gmelin , probably as a contraction of the German Essigäther , " acetic ether ". The names of esters that are formed from an alcohol and an acid, are derived from

1600-426: 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 2 and higher temperatures, converts fatty acids into fatty alcohols . Fatty alcohols are, however, more easily produced from fatty acid esters . In

1680-463: Is also an equilibrium process – essentially the reverse of the Fischer esterification reaction. Because an alcohol (which acts as the leaving group) and water (which acts as the nucleophile) have similar p K a values, the forward and reverse reactions compete with each other. As in transesterification, using a large excess of reactant (water) or removing one of the products (the alcohol) can promote

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1760-505: Is around 7.5, whereas the optimal conditions for PLA 1 activity on acidic phospholipids is around 4. The structure of a PLA 1 is a monomer that contains the following sequence: Gly-X-Ser-X-Gly, where X represents any other amino acid. The serine is considered the active site in the enzyme. PLA 1 's also contain a catalytic triad of Ser-Asp-His, with a variety of cysteine residues needed for disulfide bond formation. The cysteine residues are responsible for key structural motifs such as

1840-522: Is being applied to determine suitable growth environments for PLA 1 production. In one particular study, it was found that PLA 1 can be produced by S. cerevisiae and A. oryzae . In these PLA 1 producing cultures, increasing the nitrogen and carbon sources can lead to increase in PLA 1 yields. In the early 1900s, an observation was made, showing an accumulation of free fatty acids after incubation of pancreatic juice with phosphatidylcholine. One of

1920-648: Is considered too hazardous and expensive for large-scale applications. Carboxylic acids are esterified by treatment with epoxides , giving β-hydroxyesters: This reaction is employed in the production of vinyl ester resin from acrylic acid . Alcohols react with acyl chlorides and acid anhydrides to give esters: The reactions are irreversible simplifying work-up . Since acyl chlorides and acid anhydrides also react with water, anhydrous conditions are preferred. The analogous acylations of amines to give amides are less sensitive because amines are stronger nucleophiles and react more rapidly than does water. This method

2000-576: Is dependent on the body site the skin is covering. There are also characteristic epidermal fatty acid alterations that occur in psoriasis , atopic dermatitis , and other inflammatory conditions . The chemical analysis of fatty acids in lipids typically begins with an interesterification 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

2080-404: Is distinctive and enables animals with a keen sense of smell to differentiate individuals. The stratum corneum – the outermost layer of the epidermis – is composed of terminally differentiated and enucleated corneocytes within a lipid matrix. Together with cholesterol and ceramides , free fatty acids form a water-impermeable barrier that prevents evaporative water loss . Generally,

2160-605: Is employed only for laboratory-scale procedures, as it is expensive. Trimethyloxonium tetrafluoroborate can be used for esterification of carboxylic acids under conditions where acid-catalyzed reactions are infeasible: Although rarely employed for esterifications, carboxylate salts (often generated in situ ) react with electrophilic alkylating agents , such as alkyl halides , to give esters. Anion availability can inhibit this reaction, which correspondingly benefits from phase transfer catalysts or such highly polar aprotic solvents as DMF . An additional iodide salt may, via

2240-493: Is found in many species, it has been found that there are different classes of this one specific enzyme based on the organism being studied. There are many variations of PLA 1 , differing slightly between each organism it is present in. Most notably, it can be found in mammalian cells such as plasma of rat livers and bovine brains, and can also be found in metazoan parasites, protozoan parasites, and snake venom. Optimum pH conditions for PLA 1 activity on neutral phospholipids

2320-431: Is impervious to most free fatty acids, excluding short-chain fatty acids 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. Studies on the cell membranes of mammals and reptiles discovered that mammalian cell membranes are composed of

2400-603: Is one illustrative example. The carbonylation of methanol yields methyl formate , which is the main commercial source of formic acid . The reaction is catalyzed by sodium methoxide : In hydroesterification , alkenes and alkynes insert into the O−H bond of carboxylic acids. Vinyl acetate is produced industrially by the addition of acetic acid to acetylene in the presence of zinc acetate catalysts: Vinyl acetate can also be produced by palladium -catalyzed reaction of ethylene, acetic acid , and oxygen : Silicotungstic acid

2480-406: Is possible by 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. Fatty acids are mainly used in

Phospholipase A1 - Misplaced Pages Continue

2560-464: Is the substitution reaction between a carboxylic acid ( R−C(=O)−OH ) and an alcohol ( R'−OH ), forming an ester ( R−C(=O)−O−R' ), where R stands for any group (typically hydrogen or organyl) and R ′ stands for organyl group. Organyl esters of carboxylic acids typically have a pleasant smell; those of low molecular weight are commonly used as fragrances and are found in essential oils and pheromones . They perform as high-grade solvents for

2640-467: 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. In either numbering scheme, the position of a double bond in a fatty acid chain is always specified by giving the label of the carbon closest to

2720-501: Is the numbering scheme recommended by the IUPAC . Another convention uses letters of the Greek alphabet in sequence, starting with the first carbon after the carboxyl group. Thus carbon α ( alpha ) is C-2, carbon β ( 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 ), which

2800-504: Is used as an acyl-transfer catalyst . Another method for the dehydration of mixtures of alcohols and carboxylic acids is the Mitsunobu reaction : Carboxylic acids can be esterified using diazomethane : Using this diazomethane, mixtures of carboxylic acids can be converted to their methyl esters in near quantitative yields, e.g., for analysis by gas chromatography . The method is useful in specialized organic synthetic operations but

2880-495: Is used in the production of ethyl acetate from acetaldehyde . Esters are less reactive than acid halides and anhydrides. As with more reactive acyl derivatives, they can react with ammonia and primary and secondary amines to give amides, although this type of reaction is not often used, since acid halides give better yields. Esters can be converted to other esters in a process known as transesterification . Transesterification can be either acid- or base-catalyzed, and involves

2960-427: Is used to determine the free fatty acid content of fats; i.e., the proportion of the triglycerides that have been hydrolyzed . Neutralization of fatty acids, one form of saponification (soap-making), is a widely practiced route to metallic soaps . Hydrogenation of unsaturated fatty acids is widely practiced. Typical conditions involve 2.0–3.0 MPa of H 2 pressure, 150 °C, and nickel supported on silica as

3040-411: Is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene: The Tishchenko reaction involves disproportionation of an aldehyde in the presence of an anhydrous base to give an ester. Catalysts are aluminium alkoxides or sodium alkoxides. Benzaldehyde reacts with sodium benzyloxide (generated from sodium and benzyl alcohol ) to generate benzyl benzoate . The method

3120-506: The Finkelstein reaction , catalyze the reaction of a recalcitrant alkyl halide. Alternatively, salts of a coordinating metal, such as silver, may improve the reaction rate by easing halide elimination. Transesterification , which involves changing one ester into another one, is widely practiced: Like the hydrolysation, transesterification is catalysed by acids and bases. The reaction is widely used for degrading triglycerides , e.g. in

3200-460: The Golgi apparatus ). The "uncombined fatty acids" or "free fatty acids" found in the circulation of animals come from the breakdown (or lipolysis ) of stored triglycerides. Because they are insoluble in water, these fatty acids are transported bound to plasma albumin . The levels of "free fatty acids" in the blood are limited by the availability of albumin binding sites. They can be taken up from

3280-719: The IUPAC . Glycerides are fatty acid esters of glycerol ; they are important in biology, being one of the main classes of lipids and comprising the bulk of animal fats and vegetable oils . Lactones are cyclic carboxylic esters; naturally occurring lactones are mainly 5- and 6-membered ring lactones. Lactones contribute to the aroma of fruits, butter, cheese, vegetables like celery and other foods. Esters can be formed from oxoacids (e.g. esters of acetic acid , carbonic acid , sulfuric acid , phosphoric acid , nitric acid , xanthic acid ), but also from acids that do not contain oxygen (e.g. esters of thiocyanic acid and trithiocarbonic acid ). An example of an ester formation

Phospholipase A1 - Misplaced Pages Continue

3360-578: 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. Unsaturated fatty acids and their esters undergo auto-oxidation , which involves replacement of a C-H bond with C-O bond. The process requires oxygen (air) and is accelerated by the presence of traces of metals, which serve as catalysts. Doubly unsaturated fatty acids are particularly prone to this reaction. Vegetable oils resist this process to

3440-523: 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 is traditionally used to specify a fatty acid with double bonds at positions x , y ,.... (The capital Greek letter "Δ" ( delta ) corresponds to Roman "D", for D ouble bond). Thus, for example,

3520-485: The liver , adipose tissue , and the mammary glands during lactation. Carbohydrates are converted into pyruvate by glycolysis as the first important step in the conversion of carbohydrates into fatty acids. Pyruvate is then decarboxylated to form acetyl-CoA in the mitochondrion . However, this acetyl CoA needs to be transported into cytosol where the synthesis of fatty acids occurs. This cannot occur directly. To obtain cytosolic acetyl-CoA, citrate (produced by

3600-573: The organyl parts of the carboxylic acid and the alcohol, respectively, and R can be a hydrogen in the case of esters of formic acid . For example, butyl acetate (systematically butyl ethanoate), derived from butanol and acetic acid (systematically ethanoic acid) would be written CH 3 CO 2 (CH 2 ) 3 CH 3 . Alternative presentations are common including BuOAc and CH 3 COO(CH 2 ) 3 CH 3 . Cyclic esters are called lactones , regardless of whether they are derived from an organic or inorganic acid. One example of an organic lactone

3680-400: The reaction product . Esters are common in organic chemistry and biological materials, and often have a pleasant characteristic, fruity odor. This leads to their extensive use in the fragrance and flavor industry. Ester bonds are also found in many polymers . The classic synthesis is the Fischer esterification , which involves treating a carboxylic acid with an alcohol in the presence of

3760-751: The 20-carbon arachidonic acid is Δ , 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 between to the ω carbon (only), even in the case of multiple double bonds such as the essential fatty acids . Thus linoleic acid (18 carbons, Δ ), γ-linole n ic acid (18-carbon, Δ ), and arachidonic acid (20-carbon, Δ ) are all classified as "ω−6" fatty acids; meaning that their formula ends with –CH=CH– CH 2 – CH 2 – CH 2 – CH 2 – CH 3 . Fatty acids with an odd number of carbon atoms are called odd-chain fatty acids , whereas

3840-427: The aroma of many fruits, including apples , durians , pears , bananas , pineapples , and strawberries . Several billion kilograms of polyesters are produced industrially annually, important products being polyethylene terephthalate , acrylate esters , and cellulose acetate . Esterification is the general name for a chemical reaction in which two reactants (typically an alcohol and an acid) form an ester as

3920-423: The blood by all cells that have mitochondria (with the exception of the cells of the central nervous system ). Fatty acids can only be broken down in mitochondria, by means of beta-oxidation followed by further combustion in the citric acid cycle to CO 2 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

4000-427: The blood circulation. They are taken in through the intestine in chylomicrons , but also exist in very low density lipoproteins (VLDL) and low density lipoproteins (LDL) after processing in the liver. In addition, when released from adipocytes , fatty acids exist in the blood as free fatty acids . It is proposed that the blend of fatty acids exuded by mammalian skin, together with lactic acid and pyruvic acid ,

4080-415: The blood via intestine capillaries and travel through the portal vein just as other absorbed nutrients do. However, long-chain fatty acids are not directly released into the intestinal capillaries. Instead they are absorbed into the fatty walls of the intestine villi and reassemble again into triglycerides . The triglycerides are coated with cholesterol and protein (protein coat) into a compound called

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4160-445: The characteristic rancid odor. An analogous process happens in biodiesel with risk of part corrosion. Fatty acids are usually produced industrially by the hydrolysis of triglycerides , with the removal of glycerol (see oleochemicals ). Phospholipids represent another source. Some fatty acids are produced synthetically by hydrocarboxylation of alkenes. In animals, fatty acids are formed from carbohydrates predominantly in

4240-652: The chylomicrons can transport the triglycerides to tissues where they are stored or metabolized for energy. Fatty acids are broken down to CO 2 and water by the intra-cellular mitochondria through beta oxidation and the citric acid cycle . In the final step ( oxidative phosphorylation ), reactions with oxygen release a lot of energy, captured in the form of large quantities of ATP . Many cell types can use either glucose or fatty acids for this purpose, but fatty acids release more energy per gram. Fatty acids (provided either by ingestion or by drawing on triglycerides stored in fatty tissues) are distributed to cells to serve as

4320-420: The condensation of acetyl-CoA with oxaloacetate ) is removed from the citric acid cycle and carried across the inner mitochondrial membrane into the cytosol. There it is cleaved by ATP citrate lyase into acetyl-CoA and oxaloacetate. The oxaloacetate is returned to the mitochondrion as malate . The cytosolic acetyl-CoA is carboxylated by acetyl-CoA carboxylase into malonyl-CoA , the first committed step in

4400-420: The corresponding amides . The p K a of the alpha-hydrogens on esters of carboxylic acids is around 25 (alpha-hydrogen is a hydrogen bound to the carbon adjacent to the carbonyl group (C=O) of carboxylate esters). Many carboxylic acid esters have the potential for conformational isomerism , but they tend to adopt an S - cis (or Z ) conformation rather than the S - trans (or E ) alternative, due to

4480-465: The dehydration of mixtures of alcohols and carboxylic acids. One example is the Steglich esterification , which is a method of forming esters under mild conditions. The method is popular in peptide synthesis , where the substrates are sensitive to harsh conditions like high heat. DCC ( dicyclohexylcarbodiimide ) is used to activate the carboxylic acid to further reaction. 4-Dimethylaminopyridine (DMAP)

4560-409: The epidermal lipid matrix is composed of an equimolar mixture of ceramides (about 50% by weight), cholesterol (25%), and free fatty acids (15%). Saturated fatty acids 16 and 18 carbons in length are the dominant types in the epidermis, while unsaturated fatty acids and saturated fatty acids of various other lengths are also present. The relative abundance of the different fatty acids in the epidermis

4640-408: The first carbon atom of the organyl group replacing acidic hydrogen, is replaced by another atom from the group 14 elements ( Si , Ge , Sn , Pb ); for example, according to them, trimethylstannyl acetate (or trimethyltin acetate) CH 3 COOSn(CH 3 ) 3 is a trimethylstannyl ester of acetic acid , and dibutyltin dilaurate (CH 3 (CH 2 ) 10 COO) 2 Sn((CH 2 ) 3 CH 3 ) 2

4720-418: The first cases of observed PLA 1 activity was on 1903 when snake venom was found to alter phosphatidylcholine into lysophosphatidylcholine , which is defined as a phosphatidylcholine without one of its fatty acids. In the 1960s, it was discovered to be that enzymes catalyze this fatty acid cleavage in multiple ways, one of which is the sn -1 position. This particular reaction is catalyzed by PLA 1 , while

4800-495: The forward reaction. Basic hydrolysis of esters, known as saponification , is not an equilibrium process; a full equivalent of base is consumed in the reaction, which produces one equivalent of alcohol and one equivalent of a carboxylate salt. The saponification of esters of fatty acids is an industrially important process, used in the production of soap. Esterification is a reversible reaction. Esters undergo hydrolysis under acidic and basic conditions. Under acidic conditions,

4880-416: The hydrocarbon chain. Most naturally occurring fatty acids have an unbranched chain of carbon atoms, with a carboxyl group (–COOH) at one end, and a methyl group (–CH3) at the other end. The position of each carbon atom in the backbone of a fatty acid is 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

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4960-416: 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 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

5040-453: The lid domain and the B9 domain, both of which are lipid binding surface loops. These two loops can vary between each PLA 1 . For example, a PLA 1 enzyme with a long lid domain (22-23 amino acids) and a long B9 domain (18-19 amino acids) constitute an extracellular PLA 1 exhibiting triacylglycerol hydrolase activity. In contrast, a PLA 1 enzyme that is considered more selective will have

5120-433: The lipids (up to 70% by weight) 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 esters : triglycerides , phospholipids , and cholesteryl esters . In any of these forms, fatty acids are both important dietary sources of fuel for animals and important structural components for cells . The concept of fatty acid ( acide gras )

5200-409: The lower temperatures . The following table gives the fatty acid, vitamin E and cholesterol composition of some common dietary fats. Fatty acids exhibit reactions like other carboxylic acids, i.e. they undergo esterification and acid-base reactions. Fatty acids do not show a great variation in their acidities, as indicated by their respective p K a . Nonanoic acid , for example, has

5280-399: The main storage form of fatty acids, and thus of energy in animals. However, fatty acids are also important components of the phospholipids that form the phospholipid bilayers out of which all the membranes of the cell are constructed (the cell wall , and the membranes that enclose all the organelles within the cells, such as the nucleus , the mitochondria , endoplasmic reticulum , and

5360-707: 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 (LA) and 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 acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which can also be obtained from fish. Omega−3 and omega−6 fatty acids are biosynthetic precursors to endocannabinoids with antinociceptive , anxiolytic , and neurogenic properties. Blood fatty acids adopt distinct forms in different stages in

5440-448: The other hand, more frequently named using the systematic IUPAC name, based on the name for the acid followed by the suffix -oate . For example, the ester hexyl octanoate, also known under the trivial name hexyl caprylate , has the formula CH 3 (CH 2 ) 6 CO 2 (CH 2 ) 5 CH 3 . The chemical formulas of organic esters formed from carboxylic acids and alcohols usually take the form RCO 2 R' or RCOOR', where R and R' are

5520-468: The parent alcohol and the parent acid, where the latter may be organic or inorganic. Esters derived from the simplest carboxylic acids are commonly named according to the more traditional, so-called " trivial names " e.g. as formate, acetate, propionate, and butyrate, as opposed to the IUPAC nomenclature methanoate, ethanoate, propanoate, and butanoate. Esters derived from more complex carboxylic acids are, on

5600-927: The production of soap , both for cosmetic purposes and, in the case of metallic soaps , as lubricants. Fatty acids are also converted, via their methyl esters, to fatty alcohols and fatty amines , which are precursors to surfactants, detergents, and lubricants. Other applications include their use as emulsifiers , texturizing agents, wetting agents, 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. Ester In chemistry , an ester

5680-467: The production of fatty acid esters and alcohols. Poly(ethylene terephthalate) is produced by the transesterification of dimethyl terephthalate and ethylene glycol: A subset of transesterification is the alcoholysis of diketene . This reaction affords 2-ketoesters. Alkenes undergo carboalkoxylation in the presence of metal carbonyl catalysts. Esters of propanoic acid are produced commercially by this method: A preparation of methyl propionate

5760-440: The range 1730–1750 cm assigned to ν C=O . This peak changes depending on the functional groups attached to the carbonyl. For example, a benzene ring or double bond in conjunction with the carbonyl will bring the wavenumber down about 30 cm . Esters are widespread in nature and are widely used in industry. In nature, fats are, in general, triesters derived from glycerol and fatty acids . Esters are responsible for

5840-402: The reaction at the sn -2 position is catalyzed by phospholipase A2 . Fatty acid In chemistry , particularly in biochemistry , a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated . Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, from 4 to 28. Fatty acids are a major component of

5920-406: The reaction is the reverse reaction of the Fischer esterification . Under basic conditions, hydroxide acts as a nucleophile, while an alkoxide is the leaving group. This reaction, saponification , is the basis of soap making. The alkoxide group may also be displaced by stronger nucleophiles such as ammonia or primary or secondary amines to give amides (ammonolysis reaction): This reaction

6000-420: The reaction of an ester with an alcohol. Unfortunately, because the leaving group is also an alcohol, the forward and reverse reactions will often occur at similar rates. Using a large excess of the reactant alcohol or removing the leaving group alcohol (e.g. via distillation ) will drive the forward reaction towards completion, in accordance with Le Chatelier's principle . Acid-catalyzed hydrolysis of esters

6080-488: The rest are even-chain fatty acids. The difference is relevant to gluconeogenesis . The following table describes the most common systems of naming fatty acids. When circulating in the plasma (plasma fatty acids), not in their ester , fatty acids are known as non-esterified fatty acids (NEFAs) or free fatty acids (FFAs). FFAs are always bound to a transport protein , such as albumin . FFAs also form from triglyceride food oils and fats by hydrolysis, contributing to

6160-472: The saturated C15 and C17 derivatives, pentadecanoic acid and 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. Most common fatty acids are straight-chain compounds , with no additional carbon atoms bonded as side groups to the main hydrocarbon chain. Branched-chain fatty acids contain one or more methyl groups bonded to

6240-404: 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 triglycerides ,

6320-492: 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). 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

6400-461: Was introduced in 1813 by Michel Eugène Chevreul , though he initially used some variant terms: graisse acide and acide huileux ("acid fat" and "oily acid"). Fatty acids are classified in many ways: by length, by saturation vs unsaturation, by even vs odd carbon content, and by linear vs branched. Saturated fatty acids have no C=C double bonds. They have the formula CH 3 (CH 2 ) n COOH, for different n . An important saturated fatty acid

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