Fats and Fatty Acids

If a rapidly growing photosynthetic cell such as an alga cell is exposed to C 02 for 1 to 2 minutes and then killed, as much as 30% of the radioactive compounds formed behave as lipidlike substances when partitioned between aqueous and organic solvents. A considerable portion of the chloroplast structure consists of lipid materials, and rapid lipid synthesis is required for chloroplast growth and division. 

The starting point for synthesis of fatty acids and other lipoid substances such as carotenoids and terpenes is acetyl coenzyme A. Very little labeled acetic acid can be isolated from the photo-synthesizing cell. It is presumed that the concentration of acetyl coenzyme A is very small and that the small pool turns over very rapidly. 

A plausible pathway to acetyl coenzyme A from the carbon cycle would be via a phosphoroplastic splitting of the thiamine pyro-phosphate-glycolaldehyde compound formed by the transketolase reaction. Such a split [Eq. (26)] could be mediated by an enzyme 

Once acetyl coenzyme A has been formed, subsequent reactions leading to fatty acid synthesis are probably similar to those which occur in other biosynthetic systems (Calvin and Bassham, 1962). In the chloroplast these reactions may be photosynthetic reactions in that they employ ATP and reduced pyridine nucleotide cofactors formed by the photochemical reactions of photosynthesis. 

The fatty acids thus photosynthesized are then esterified with glycerol or glycerol phosphate formed directly from triose phosphate of the carbon reduction cycle [Eq. (27)]. Galactolipids 

The naturally occurring fatty acids are carboxylic acids with unbranched hydrocarbon chains of 4-24 carbon atoms. They are present in all organisms as components of fats and membrane lipids, in these compounds, they are esterified with alcohols (glycerol, sphingosine, or cholesterol). However, fatty acids are also found in small amounts in unesterified form. In this case, they are known as free fatty adds (FFAs). As free fatty acids have strongly amphipathic properties (see p. 28), they are usually present in protein-bound forms. 

The table lists the full series of aliphatic carboxylic acids that are found in plants and animals. In higher plants and animals, unbranched, longchain fatty acids with either 16 or 18 carbon atoms are the most common— e.g., palmitic and stearic acid. The number of carbon atoms in the longer, natural fatty acids is always even. This is because they are biosynthesized from C2 building blocks (see p.168). 

Some fatty acids contain one or more isolated double bonds, and are therefore unsaturated. Common unsaturated fatty acids 

Essential fatty acids are fatty acids that have to be supplied in the diet. Without exception, these are all polyunsaturated fatty acids the C20 fatty acid arachidonic add (20 4 5,8,11,14) and the two Cis acids linoleic add (18 2 9,12) and linolenic add (18 3 9,12,15). The animal organism requires arachidonic acid to synthesize eicosanoids 

Fats are esters of the trivalent alcohol glycerol with three fatty acids. When a single fatty acid is esterified with glycerol, the product is referred to as a monoacylglycerol (fatty acid residue = acyl residue). 

---

Fatty Acid and Fats. What Makes Good Soap . 157... 

Several lipids are not formed independently in the human body. These substances, as essential fatty acids and fat-soluble vitamins, are indispensable components of nutrition (see pp.364ff.)... 

Fat synthesis in the liver (right). Fatty acids and fats are mainly synthesized in the liver and in adipose tissue, as well as in the kidneys, lungs, and mammary glands. Fatty acid biosynthesis occurs in the cytoplasm—in contrast to fatty acid degradation. The most important precursor is glucose, but certain amino acids can also be used. 

Patients with primary chylomicronemia and some with mixed lipemia must consume a diet severely restricted in total fat (10-20 g/d, of which 5 g should be vegetable oils rich in essential fatty acids), and fat-soluble vitamins should be given. 

The stability of the material was verified at -20°C, +20°C and +35°C by the determination of the CB congeners over a period of 12 months. In addition, the stability of the dry mass, free fatty acids and fat content was monitored as key indicators of the stability of the matrix. The results showed that the CB congeners were stable at the three temperatures tested, as well as the matrix components. 

One of the most common uses of IR spectroscopy in the analysis of fatty acids and fats is the determination of fmn -unsaturation. An interesting procedure for tran5-unsaturation using IR attenuated total reflectance (ATR) spectroscopy has been described (Sipos and Ackman, 1978). The samples do not have to be weighed or diluted. A special ATR cell is used to make readings at 10.3 / m. The system can be used to monitor a continuous flow system, and the presence of catalyst does not affect the readings. 

The regulation of mammalian acetyl-CoA carboxylase has been well studied owing to the key role of this enzyme in controlling overall fatty acid (and fat) synthesis. Control occurs in two ways-short-term control which involves allosteric regulation and covalent enzyme modification or long-term control where the amounts of the carboxylase are... 

There are two aspects to lipid requirements in the human diet-these are qualitative and quantitative. Firstly, certain lipids are needed for good health-essential fatty acids and fat-soluble vitamins are good examples. Secondly, it is usually considered that, in the normal diet, some 25-30% of the total calories are conveniently supplied as fat (Jones, 1974). Such lipid (in reasonable amounts) also usually makes food more palatable. 

D. 2009. Cahfomia Hass avocado Profiling of carotenoids, tocopherol, fatty acid, and fat content during maturation and from different growing areas. J. Agric. Food Chem. 57 10408-10413. 

Poynten, A.M., Gan, S.K., Kiiketos, A.D., O Sullivan, A., Kelly, J.J., Ellis, B.A., Chisholm, D.J., and Campbell, L.V., 2003. Nicotinic acid-induced insulin resistance is related to increased circulating fatty acids and fat oxidation but not muscle lipid content. Metabolism. 52 699-704. 

Suitable fatty acids and fatly alcohols comprise a carbon chain having from 12 to 22 carbon atoms. Preferred fatty acids include stearic acid, palmitic acid, and their combinations. Suitable derivatives include salts of the fatty acids. 

Direct ethoxylation of fatty acids and fats with conventional catalysts yields a complex mixture of mono- and diesters, as well as various polyethylene glycols as by-products, with a wide range in the number of polyethylene glycol units. Despite the inhomogeneity of the composition of the final product, they have found a wide use as emulsifiers in food, feed and technical applications and detailed studies of their emulsification and solubility/dispersibility properties have been carried out [57-59],... 

---