Lipid, compound

Steroids (1) are members of a large class of lipid compounds called terpenes that are biogenicaHy derived from the same parent compound, isoprene, C Hg Steroids contain or are derived from the perhydro-l,2-cyclopentenophenanthrene ring system (1) and are found in a variety of different marine, terrestrial, and synthetic sources. The vast diversity of the natural and synthetic members of this class depends on variations in side-chain substitution (primarily at C17), degree of unsaturation, degree and nature of oxidation, and the stereochemical relationships at the ring junctions. 

Glyoxylate cycle A modification of the Krebs cycle, which occurs in some bacteria. Acetyl coenzyme A is generated directly from oxidation of fatty acids or other lipid compounds. 

Until recently no enzymes able to produce olivetol-like compounds have been isolated. In an article by Puna et al., polyketide III enzymes were responsible for the formation of phenohc lipid compound [34], a natural product group that ohvetol belongs to. Although the biosynthesized compounds contained a longer chain, which increased over time, the study supported the hypothesis of olivetohc acid production by a polyketide III synthase. Further studies on the genetic and protein level are essential to elucidate the mode of mechanism by which olivetohc acid is formed in C. sativa. 

Lipids have been dehned on the basis of their stmctnre and solnbility. Lipids are natnrally occnrring componnds consisting of fatty acids and their derivatives, bile acids, pigments, vitamins, and steroids, as well as terpenoids, which are usually soluble in organic solvents such as benzene, chloroform, ether, and alcohol, etc., with variable solubility depending on the stmctnre of the lipid compound. 

Table 7.1 Ions for trimethylsilyl (TMS) and t butyldi methyl si lyl (TBDMS) derivatives of lipid compounds useful for quantitation in selected ion monitoring...

Sugars/polysaccharides Unsaturated lipid compounds L-Amino acids/peptides Nucleotides, bases, etc. Biopolymers... 

Simoneit BRT, Gardoso JN, Robinson N, An assessment of terrestrial higher molecular tveight lipid compounds in air particulate matter over the South Atlantic from about 30—70°S, Chemosphere 23 447 65, 1991. 

Simoneit, B. R. T., J. N. Cardoso, and N. Robinson, An Assessment of Terrestrial Higher Molecular Weight Lipid Compounds in Aerosol Particulate Matter over the South Atlantic from about 30-70°S, Chemosphere, 23, 447-465 (1991b). 

The calcium-independent ATPase of the lipid modified preparations is not only different from the calcium-dependent ATPase but also from the calcium-independent ATPase of native preparations — the basic ATPase — which has a lower nucleotide specificity126. The experiments in which the lipid matrix of the sarcoplasmic membranes has been replaced by lipid compounds not present in native membranes reveal a high degree of functional flexibility of the enzyme. On the other hand, a few residual lipids in the protein are sufficient to prevent these changes in the structure of the enzyme and to preserve its calcium sensitivity. 

In summary, phospholipids (phosphatides) comprise a group of lipid compounds that yield, upon hydrolysis, phosphoric acid, an alcohol, fatty acid, and a nitrogenous base. They are widely distributed throughout nature. 

Steroids are members of a large class of lipid compounds called terpenes. Using acetate as a starting material, a variety of organisms produce terpenes by essentially Lire same biosynlheLic scheme (Fig. 3). The sell-condensation of two molecules of acetyl coenzyme A (CoA) forms acetoacetyl CoA. Condensation of acetoacetyl CoA with a third molecule of acetyl CoA, then followed by an NADPH-mediated reduction of the thioester moiety produces mevalonic acid (22). Phosphorylation of (22) followed by concomitant decarboxylation and dehydration processes... 

Lipid samples from natural sources generally contain various classes of lipid compounds in which concentration of individual lipid class varies substantially. Lipids from fat-rich tissues of biological samples are usually dominated by triglycerides. On the other hand, those from low-fat tissues tend to have even distribution of compounds among lipid classes. The range of calibration standard solutions described in this unit is the same for all lipid classes. To improve the accuracy in lipid-class quantification, it would always be a good approach to adjust the range of individual calibration standards based on the lipid class profile of lipids from particular sources. 

One of the disadvantages of using TLC-FID in the quantitation of lipid compounds is the low precision in spotting fixed volumes of sample solution onto the Chromarods, which results in variations in the quantitation of lipid classes. This problem can be minimized if all calibration standards are dissolved in one solution and if calibration is performed using the same set of Chromarods used for the lipid samples. 

Synthesis of most phospholipids starts from glycerol-3-phosphate, which is formed in one step from the central metabolic pathways, and acyl-CoA, which arises in one step from activation of a fatty acid. In two acylation steps the key compound phosphatidic acid is formed. This can be converted to many other lipid compounds as well as CDP-diacylglycerol, which is a key branchpoint intermediate that can be converted to other lipids. Distinct routes to phosphatidylethanolamine and phosphatidylcholine are found in prokaryotes and eukaryotes. The pathway found in eukaryotes starts with transport across the plasma membrane of ethanolamine and/or choline. The modified derivatives of these compounds are directly condensed with diacylglycerol to form the corresponding membrane lipids. Modification of the head-groups or tail-groups on preformed lipids is a common reaction. For example, the ethanolamine of the head-group in phosphatidylethanolamine can be replaced in one step by serine or modified in 3 steps to choline. 

Beeswax is a simple ester of fatty acid and a long chain alcohol. Ear wax contains trigycerides, esters of glycerol and three fatty acids, among other lipid compounds. 

Rezanka T, Dembitsky V (1999) Novel Brominated Lipidic Compounds from Lichens of Central Asia. Phytochemistry 51 963... 

The silk and cuticle of spiders are covered by a lipid layer. These lipid compounds protect from external damaging factors such as humidity, which modifies the cuticle s or silk s physical properties. The frequency of water exposure in natural circumstances suggests that wetting with water or similar solvents must have negligible or manageable effects on pheromone function. 

Quantitative changes in lipid compounds on the silk and cuticle of females correlate significantly with changes in female sexual receptivity in spiders. For example, female T. atrica attach a contact sex pheromone to their web (Trabalon et al., 1997,2005 Prouvost et al., 1999). This pheromone consists of a complex mixture of saturated hydrocarbons, methyl esters (methyl tetradecanoate, methyl pentadecanoate, methyl hexadecanoate, and methyl octadecanoate) and their fatty acids (tetradecanoic, pentadecanoic, hexadecanoic, and cis,cis-9,12-octadecadienoic acids). The female uses cuticular compounds, which are applied to the silk in substantial amounts during web construction. Modification of chemical profiles makes the female attractive to males (Trabalon et al., 2005). Receptive females are different to unreceptive ones with respect to three fatty acids (hexadecanoic, octadeca-dienoic and octadecenoic acids) and three methyl esters (linoleate, oleate, and stearate) present on both the web and the cuticle. Our combined results from chemical analyses and behavioral assays demonstrate clearly that these contact compounds are quantitatively correlated with the behavior of spiders. 

Canuel et al., 1997). This recurring theme of overlapping sterol markers in different organic matter sources indicates that caution should be advised when using sterols solely to distinguish between land and aquatic sources (Volkman, 1986 Jaffe et al., 2001). Instead, biomarker source identifications should be corroborated across lipid compound classes and using bulk and compound-specific isotope analysis. 

Canuel, E.A., and Martens, C.S. (1996) Reactivity of recently deposited organic matter degradation of lipid compounds near the sediment-water interface. Geochim. Cosmochim. Acta 60, 1793-1806. 

Rontani JF. Photodegradation of lipidic compounds during the senescence of phytoplak-ton. In Boule P, ed. Environmental Photochemistry. Berlin Springer-Verlag, 1999 263-84. 

Functionality and physiological effects of seaweed lipid compounds 473... 

FUNCTIONALITY AND PHYSIOLOGICAL EFFECTS OF SEAWEED LIPID COMPOUNDS 473... 

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