Fatty even numbered

The fatty acids occur in nature chiefly as glycerides see fats), which constitute the most important part of the fats and oils, and as esters of other alcohols, the waxes. The naturally occurring fatty acids are mostly the normal straight-chain acids with an even number of carbon atoms. 

Acetyl coenzyme A is the biosynthetic precursor to the fatty acids, which most often occur naturally as esters Fats and oils are glycerol esters of long chain carboxylic acids Typically these chains are unbranched and contain even numbers of carbon atoms... 

Fats and oils (Section 26 2) Tnesters of glycerol Fats are solids at room temperature oils are liquids Fatty acid (Section 26 2) Carboxylic acids obtained by hydro lysis of fats and oils Fatty acids typically have unbranched chains and contain an even number of carbon atoms in the range of 12-20 carbons They may include one or more double bonds... 

Fatty acids derived from animal and vegetable sources generally contain an even number of carbon atoms siace they are biochemically derived by condensation of two carbon units through acetyl or malonyl coenzyme A. However, odd-numbered and branched fatty acid chains are observed ia small concentrations ia natural triglycerides, particularly mminant animal fats through propionyl and methylmalonyl coenzyme respectively. The glycerol backbone is derived by biospeciftc reduction of dihydroxyacetone. 

In recent years, especially in the USSR and Europe, synthetic fatty acids, prepared via hydrocarbon oxidation, have been used to prepare fatty amines (2,9). In 1978 Eastern Europeans produced an estimated 0.55 biUion kg of synthetic fatty acids with odd and even numbers of carbon atoms, whereas in the United States, production of natural fatty acids with even carbon atom chain-length acids was 435 million kg. To date, there has been no significant production of synthetic fatty acids in the United States. 

The solubihty of water in fatty acids, 0.92% for stearic acid at 68.7°C, is greater than the solubiHty of the acid in water, 0.0003% for stearic acid at 20°C, and this solubihty tends to increase with increasing temperature (21). SolubiHties of aHphatic acids in organic solvents demonstrate another example of the alternating effect of odd vs even numbered acids (Table 8). 

FIGURE 8.1 The structures of some typical fatty acids. Note that most natural fatty acids coutaiu au even number of carbon atoms and that the double bonds are nearly always ck and rarely conjugated. 

He observed that fatty acid analogs with even numbers of carbon atoms yielded phenyl acetate, whereas compounds with odd nnmbers of carbon atoms produced only benzoate. 

In essence, this series of four reactions has yielded a fatty acid (as a CoA ester) that has been shortened by two carbons, and one molecule of acetyl-CoA. The shortened fatty acyl-CoA can now go through another /3-oxidation cycle, as shown in Figure 24.10. Repetition of this cycle with a fatty acid with an even number of carbons eventually yields two molecules of acetyl-CoA in the final step. As noted in the first reaction in Table 24.2, complete /3-oxidation of palmitic acid yields eight molecules of acetyl-CoA as well as seven molecules of FADHg and seven molecules of NADFI. The acetyl-CoA can be further metabolized in the TCA cycle (as we have already seen). Alternatively, acetyl-CoA can also be used as a substrate in amino acid biosynthesis (Chapter 26). As noted in Chapter 23, however, acetyl-CoA cannot be used as a substrate for gluco-neogenesis. 

Most fatty acids have an even number of carbon atoms, so none are left over after /3-oxidation. Those fatty acids with an odd number of carbon atoms yield the three-carbon propionyl CoA in the final j3-oxidation. Propionyl CoA is then converted to succinate by a multistep radical pathway, and succinate enters the citric acid cycle (Section 29.7). Note that the three-carbon propionyl group should properly be called propnnoyl, but biochemists generally use the non-systematic name. 

One of the most striking features of the common fatty adds is that they have an even number of carbon atoms (Table 27.1, p. 1062). This even number results because all fatty acids are derived biosynthelically from acetyl CoA by sequential addition of two-carbon units to a growing chain. The acetyl CoA, in turn, arises primarily from the metabolic breakdown of carbohydrates in the glycolysis pathway that weTl see in Section 29.5. Thus, dietary carbohydrates consumed in excess of immediate energy needs are turned into fats for storage. 

Write the equation for the final step in the /3-oxidation pathway of any fatty acid with an even number of carbon atoms. 

The fatty adds commonly encountered in biological systems are straight chained alkanoic or alkenoic adds, containing an even number of carbon atoms (usually Ch-Ch). natural n Senera / these fatty adds can be produced readily by extraction of the lipids from sources natural sources and saponifying the neutral triglycerides. This is satisfactory providing a mixture of fatty acids is acceptable. Purification of spedfic fatty adds from the saponification mixture increases the costs considerably. 

Linear, even-numbered, primary alcohols—like the natural fatty alcohols—are produced by the aluminum organic alcohol synthesis after Ziegler, the so-called Alfol process. This alcohol synthesis proceeds in three steps ... 

Because fatty alcohols can easily be converted to the corresponding chlorides or bromides, they are a useful starting material for surface-active phosphonic acid derivatives. A variety of n-alkoxymethylphosphonic acids possessing surface-active properties were synthesized from fatty alcohols having an even number of carbon atoms (Cl2-C18) [98] see Eqs. (34)-(36). 

Primary alcohols are produced either by the catalytic hydrogenation of methyl esters or by fatty acids derived from oils and fats, e.g., coconut oil (C12-C14) or tallow (Cl6-C18), or from synthetic sources. Alcohols manufactured from natural oils and fats and from the Ziegler-type processes produce even-numbered chain length primary alcohols. 

Fatty acids occur mainly as esters in natural fats and oils but do occur in the unesterified form as free fatty acids, a transport form found in the plasma. Fatty acids that occur in natural fats are usually straight-chain derivatives containing an even number of carbon atoms. The chain may be saturated (containing no double bonds) or unsaturated (containing one or more double bonds). 

The melting points of even-numbered-carbon fatty acids increase with chain length and decrease according to unsaturation. A triacylglycerol containing three sam-rated fatty acids of 12 carbons or more is solid at body temperature, whereas if the fatty acid residues are 18 2, it is liquid to below 0 °C. In practice, natural acylglyc-erols contain a mixture of fatty acids tailored to suit their functional roles. The membrane lipids, which must be fluid at all environmental temperatures, are... 

Of the two major phosphohpid classes present in membranes, phosphoglycerides are the more common and consist of a glycerol backbone to which are attached two fatty acids in ester linkage and a phosphorylated alcohol (Figure 41-2). The fatty acid constiments are usually even-numbered carbon molecules, most commonly containing 16 or 18 carbons. They are unbranched and can be saturated or unsamrated. The simplest phosphoglyceride is phosphatidic acid, which is... 

Fatty acids of plant, animal, and microbial origin usually consist of an even number of carbon atoms in the straight chain. The number of carbon atoms of fatty adds in animals may vary from 2 to 36, whereas some microorganisms may contain 80 or more carbon atoms. Also, fatty adds of animal origin may have one to six ds double bonds, whereas those of higher plants rarely have more than three double bonds. Fatty adds also may be saturated, monounsaturated (monoenoic), or polyunsaturated (polyenoic) in nature. Some fatty acids may consist of branched chains, or they may have an oxygenated or cyclic structure. 

The oxidation products of an even-numbered fatty acid are acetyl-CoA, FAD H2 and NAD H2. Subsequently, acetyl-CoA enters the Krebs cycle, and FAD H2 and NAD H2 are directly supplied to the respiratory chain. 

Energy Balance of Fatty Acid Oxidation. The energetic value of an even-numbered fatty acid is estimated in the following manner. Complete oxidation of a fatty acid composed of 2n carbon atoms yields... 

The end product of the intermediary metabolism of fatty acids with an uneven number of carbons differs sharply from those formed after the breakdown of the even-chain fatty acids. Whereas glycogen is produced from the fatty acids having an uneven number of carbon atoms, those fatty acids with an even number of carbon atoms have no glycogenic activity, but, with the possible exception of acetic acid, they are all ketogenic and possess no ketolytic activity. 

Although there are some reports to the contrary, the evidence on the whole would seem to indicate that the straight chain fatty acids with an even number of carbon atoms are entirely ineffective as sources of carbohydrate. With the possible exception of acetic acid, the administration of the even-numbered fatty acids uniformly gives rise to a ketonuria,63 64 while it has been demonstrated repeatedly that substances convertible to carbohydrate counteract an existing ketonuria. 

Although glycogenesis has been shown to follow the administration of some synthetic triglycerides of even-numbered fatty acids, it was shown above that this only occurs with triglycerides incapable of storage in the animal body, and then only to an amount corresponding to that which would be produced by the glycerol moiety of the fat. 

Their hydrophobicity and their plasticity were appreciated and used for a long time in a wide range of activities. To our knowledge, the first wax to have been exploited is beeswax. Beeswax is produced by various species of bees in the world, and it has a melting point between 62°C and 64°C. It mainly contains homologous series of even-numbered fatty acids (C22 C34, C2 being the predominat compound), odd-numbered ra-alkanes (C2i C33, C27 being the major compound) and even-numbered palmitic esters from C40 to C52 (Tulloch and Hoffman, 1972 Kolattukudy, 1976). Hydroxy esters, diesters and hydroxy diesters also form part of beeswax to a lesser extent. 

Beeswax Produced by bees Even numbered fatty acids (C22 C34) Odd numbered n alkanes (C2i C33) Even numbered palmitic esters (C40 C52)... 

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