Fatty acids predominant

Sohd fats may show drastically different melting behavior. Animal fats such as tallow have fatty acids distributed almost randomly over all positions on the glycerol chain. These fats melt over a fairly broad temperature range. Conversely, cocoa has unsaturated fatty acids predominantly in the 2 position and saturated acids in the 1 and 3 positions. Cocoa butter is a brittle sohd at ambient temperature but melts rapidly just below body temperature. 

TAG-CH3 and TAG-CH2-, acyl chain terminal-CH3 and bulk (-CH2-)n groups, respectively, of fatty acids (predominantly triacylglycerols) associated with chylomicron- and very low-density lipoprotein (VLDL) Thr, threonine-CHs Val, valine-CHs. The asterisk In spectrum (b) denotes a radiolytically-generated 2.74 p.p.m. 

Polyunsaturated fatty acids are characterized by a large number of C = C double bonds in their hydrocarbon chain. Stearic acid has no C = C double bonds and therefore is not unsaturated, let alone polyunsaturated. But eleostearic acid has three C = C double bonds and thus is polyunsaturated. Polyunsaturated fatty acids are recommended in dietary programs since saturated fats are linked to a high incidence of heart disease. Of the lipids listed in Table 28-2, safflower oil has the highest percentage of unsaturated fatty acids, predominately linoleic acid, an unsaturated fatty acid with two C=C bonds. 

Most natural triacylglycerols do not have a random distribution of fatty acids on the glycerol backbone. In plant oils, unsaturated acids predominate at the sn-2 position, with more saturated acids at sn-l and sn-3. The distribution of fatty acids at the sn-l and sn-3 positions is often similar, although not identical. However, a random distribution between these two positions is often assumed as full stereospecific analysis is a time-consuming specialist procedure. In animal fats, the type of fatty acid predominating at the sn-2 position is more variable for example, palmitate may be selectively incorporated as well as unsaturated acids (Table 5). 

This compound is the zinc salt of a mixture of fatty acids, predominantly lauric acid, which is one of the three most widely distributed saturated fatty acids found in nature (coconut and palm oils). Consequently, no hazardous environmental impact is expected. 

Other studies have indicated that PG and PLD are a major source of PA in cells stimulated with various agonists [197-200] and several studies have confirmed biphasic formation of DAG, with the first phase derived from PIP2 and the second from PC via PA [201-205]. Analyses of the specific fatty acid composition of PA and PtdBut derived from cells treated with butanol and stimulated by bombesin or LPA also showed a predominance of saturated and mono-unsaturated fatty acids in the lipids derived from PLD action [206]. The fatty acid composition was very different from that found in DAG generated by PLC action on PIP2, in which polyunsaturated fatty acids predominate. The key issue is whether the DAG species derived from PC can activate PKC. Although studies indicate that this species is active on PKC in vitro, this has not been demonstrated in vivo. As described above [196], PC-derived DAG can activate Ca +-independent PKC isozymes but, because of the lack of a Ca rise, it cannot activate ( a -dcpcridcril PKC isozymes. 

The amount of VLDL secreted by the liver is extremely variable and can be affected in a number of ways. A primary determinant of VLDL output is the flux of free fatty acids entering the liver. The liver responds to an increase in free fatty acids by synthesis of more and larger VLDLs. If saturated fatty acids predominate in the formation of triacylglycerol, the VLDL particles will be more numerous but smaller than if polyunsaturated fatty acids predominate. This finding may be related to the reduction in plasma cholesterol levels that results from elevating the proportion of polyunsaturated fats in the diet. The surface-to-volume ratio is smaller in the larger VLDLs. Since cholesterol... 

The polymorphic behaviour of a fat is determined to a large extent by the fatty acids within the TAGs. Fats which are composed of fatty acids predominantly of... 

The mammary gland produces milk, which is the major source of nutrients for the breastfed human infant. The fatty acid composition of human milk varies, depending on the diet of the mother. However, long-chain fatty acids predominate, particularly palmitic, oleic, and linoleic acids. Although the amount of fat contained in human milk and cow s milk is similar, cow s milk contains more short- and medium-chain fatty acids and does not contain the long-chain, polyunsaturated fatty acids found in human milk that are important in brain development. 

The fatty acid synthetase of Brevibacterium ammoniagenes has a high molecular weight (like Type I synthetases) but produces both saturated and unsaturated acids (like E, coli Type II synthetase). In most Gram-positive and some Gram-negative bacteria, branched-chain fatty acids predominate. These branched-chain acids are made by Type II synthetases that use short-chain branched acyl-CoA primers instead of acetyl-CoA and so produce iso or anteiso fatty acid products (Kaneda, 1977). 

Unsaturated fatty acids predominate in plant tissues, and oxygenated acids are major components of some seed oils. The classic 8-oxidation path-... 

The oil bodies of C. abyssinica synthesized fatty acids from [ Cjmalonyl-CoA and triacylglycerols from [ C]palmitoyl-CoA or [ C]glycerol-3-P (Gurr et al., 1974). Evidence that this was not due to contamination was, first, that the fat fraction synthesized a pattern of fatty acids (predominantly erucic acid) totally different from that of other subcellular fractions and, second, that of all the fractions tested only the fat fraction had an appreciable specific activity for triacylglycerol biosynthesis. In ultrastructural studies, no inclusions could be seen in Crambe oil bodies, and it was concluded that the enzymes were contained in a bounding membrane or in granular material that was always associated with the oil body fraction (Fig. 12). 

Table III presents fatty acid analyses for ASG. It is apparent that the predominant fatty acid is either 16 0 or 18 2. Both in leaves and in other plant parts, one or the other of these fatty acids predominates. In most cases, when either 16 0 or 18 2 is the most abundant fatty acid, the other of the pair is the second most abundant. Are these distributions a reflection of structural requirements for the function of ASG A reflection of enzyme specificity for certain fatty acids Or a reflection of the availability of an acyl donor Some of these questions will be taken up in Section 1II,B.

Vitamin D is absorbed in the lower portion of the intestine after uptake of the sterol by the mucosal tissue, and it is transferred to the lymph. Like vitamin A, vitamin D is esterified in the intestinal mucosa. Esterification occurs with a number of fatty acids, predominantly palmitate, but also stearate, linoleate, oleate, andmyronate. Again like vitamin A, vitamin D is stored in the liver in the form of the ester. Two other groups of vitamin D metabolites are also known excretory products (glucuronide and bile acid derivatives) and active forms (hydroxylated derivatives). A portion of vitamin D is excreted in the bile where it appears conjugated either to glucuronides or to tau-rocholic acid [10]. 

Chemical synthesis of the palmitoyl- and stearoyl-derivatives of dihydrosphingomyelin confirmed this structure (Shapiro et al. 1958). Long chain saturated fatty acids, mono- and even diunsaturated fatty acids (predominantly stearic, lignoceric and nervonic acids) have been isolated from sphingomyelin, but no hydroxy fatty acids (Sweeley 1963 Kishimoto et al. 1963 O Brien et al. 1964). 

Acetyl CoA is produced by the catabolism of carbohydrates, fats, and certain amino acids. The catabolism of fatty acids predominates over the catabolism of carbohydrates in certain illnesses, such as diabetes. When there is not enough oxaloacetate to react with the available CoA, a Claisen condensation of two acetyl CoA molecules produces acetoacetyl CoA. 

Saturated and unsaturated acids, such as palmitic, stearic, palmit-oleic, oleic, linoleic, and linolenic, are the major components of common seed oils other saturated and unsaturated acids are often present as major or minor components sometimes in specific seeds, unusual fatty acids predominate the component acids of seed fats could themselves be a basis for a classification of plants (Hilditch and Williams, 1964). Table I shows the composition of some of the most common seed oils. 

Perhaps the most significant aspect of lipids in the human diet is their content of different types of fatty acids saturated, monounsaturated and polyunsaturated (section 3.1). It is important to point out at the outset that all natural fats contain complex mixtures of all three types of fatty acids. It is incorrect to describe a fat as saturated or polyunsaturated only the constituent fatty acids can be so described. Yet fats in which the saturated acids form the largest single fraction are frequently categorized as saturated fats to contrast them with fats in which polyunsaturated fatty acids predominate. As an example of where this can be misleading to a layman, lard is frequently categorized as a saturated fat, yet over half (about 55%) of the fatty acids are unsaturated (Table 4.1). 

Seed oils contain a wide variety of fatty acids, the composition of which is characteristic of the family to which the plant belongs. Generally one fatty acid predominates (Table 4.2). It may either be one of the normal fatty acids, palmitic, oleic, or linoleic, as exemplified by palm oil, olive oil and sunflower seed oil or it may be an unusual acid, for example erucic acid in older varieties of rape seed oil. Coconut oil and palm kernel oil are unusual among seed oils in having a preponderance of saturated fatty acids in which the acids of medium chain length predominate. It is therefore an unjustified generalization to characterize all vegetable oils as unsaturated. 

In section 3.4 we described the biosynthesis of eicosanoids from polyunsaturated fatty acids of the n-3 and n-6 families and indicated in section 3.4.8 that the balance of eicosanoids produced was important in, for example, maintaining normal vascular function. Several studies have demonstrated that altering the amounts and types of n-6 and n-3 fatty acids in the diet can influence the spectrum of eicosanoids produced. For example, substitution of fish oils in which n-3 polyunsaturated fatty acids predominate for diets in which linoleic acid (n-6) is the main polyunsaturated fatty acid (as typified by the UK diet) results in changes in plasma and platelet fatty acid profiles from arachidonic to eicoasapentaenoic acid as the predominant polyunsaturated fatty acid and a reduction in the formation by platelets of thromboxane A2, an eicosanoid that stimulates their aggregation (Table 5.7). 

---