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| Abbreviations | |
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| Preface | |
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| Acknowledgements | |
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| Lipids: definition, isolation, separation and detection | |
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| Introduction | |
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| Definitions | |
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| Structural chemistry and nomenclature | |
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| Extraction of lipids from natural samples | |
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| Likely components of the crude lipid extract | |
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| General features of lipids important for their analysis | |
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| Chromatographic techniques for separating lipids | |
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| The two phases can be arranged in a variety of ways | |
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| Gas-liquid chromatography is a particularly useful method for volatile derivatives of lipids | |
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| Absorption column chromatography is used for the separation of large amounts of lipids | |
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| Thin layer absorption chromatography can achieve very good separation of small lipid samples | |
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| Other useful methods | |
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| Summary | |
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| Further Reading | |
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| Fatty acid structure and metabolism | |
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| Structure and properties | |
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| Saturated fatty acids | |
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| Branched-chain fatty acids | |
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| Unsaturated fatty acids | |
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| Monoenoic (monounsaturated) fatty acids | |
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| Polyenoic (polyunsaturated) fatty acids | |
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| Cyclic fatty acids | |
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| Oxy acids | |
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| Conjugated unsaturated fatty acids | |
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| Fatty aldehydes and alcohols | |
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| Some properties of fatty acids | |
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| Quantitative and qualitative fatty acid analysis | |
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| General principles | |
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| Determination of the structure of an unknown acid | |
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| The biosynthesis of fatty acids | |
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| Conversion of fatty acids into metabolically active thiolesters is often a prerequisite for their metabolism | |
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| Acyl-CoA thiolesters were the first types of activated fatty acids to be discovered | |
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| Acyl-acyl carrier proteins can be formed as distinct metabolic intermediates in some organisms | |
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| The biosynthesis of fatty acids can be divided into de novo synthesis and modification reactions | |
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| De novo biosynthesis | |
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| Acetyl-CoA carboxylase | |
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| Fatty acid synthase | |
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| Termination | |
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| Elongation | |
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| Branched-chain fatty acids | |
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| The biosynthesis of hydroxy fatty acids results in hydroxyl groups in different positions along the fatty chain | |
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| The biosynthesis of unsaturated fatty acids is mainly by oxidative desaturation | |
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| Monounsaturated fatty acids | |
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| Polyunsaturated fatty acids | |
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| Formation of polyunsaturated fatty acids in animals | |
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| Biohydrogenation of unsaturated fatty acids takes place in rumen microorganisms | |
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| The biosynthesis of cyclic acids provided one of the first examples of a complex lipid substrate for fatty acid modifications | |
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| The control of fatty acid synthesis can take place at a number of enzyme steps | |
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| Acetyl-CoA carboxylase (ACC) regulation in animals | |
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| Acetyl-CoA carboxylase regulation in other organisms | |
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| Regulation of fatty acid synthase | |
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| Control of animal desaturases | |
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| Degradation of fatty acids | |
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| [beta]-Oxidation is the most common type of biological oxidation of fatty acids | |
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| Cellular site of [beta]-oxidation | |
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| Transport of acyl groups to the site of oxidation: the role of carnitine | |
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| Control of acylcarnitine formation is very important | |
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| Enzymes of mitochondrial [beta]-oxidation | |
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| Other fatty acids containing branched chains, double bonds and an odd number of carbons atoms can also be oxidized | |
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| Regulation of mitochondrial [beta]-oxidation | |
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| Fatty acid oxidation in E. coli | |
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| [beta]-Oxidation in microbodies | |
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| [alpha]-Oxidation of fatty acids is important when structural features prevent [beta]-oxidation | |
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| [omega]-Oxidation uses mixed-function oxidases | |
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| Chemical peroxidation is an important reaction of unsaturated fatty acids | |
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| Peroxidation catalysed by lipoxygenase enzymes | |
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| Lipoxygenases are important for stress responses and development in plants | |
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| Essential fatty acids and the biosynthesis of eicosanoids | |
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| The pathways for prostaglandin synthesis are discovered | |
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| Cyclic endoperoxides can be converted into different types of eicosanoids | |
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| New eicosanoids are discovered | |
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| The cyclooxygenase products exert a range of activities | |
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| Prostaglandins and other eicosanoids are rapidly catabolized | |
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| Instead of cyclooxygenation, arachidonate can be lipoxygenated or epoxygenated | |
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| Control of leukotriene formation | |
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| Physiological action of leukotrienes | |
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| For eicosanoid synthesis an unesterified fatty acid is needed | |
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| Essential fatty acid activity is related to double bond structure and to the ability of such acids to be converted into a physiologically active eicosanoid | |
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| Summary | |
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| Further Reading | |
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| Lipids as energy stores | |
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| Introduction | |
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| The naming and structure of the acylglycerols (glycerides) | |
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| Triacylglycerols are the major components of natural fats and oils; partial acylglycerols are usually intermediates in the breakdown or synthesis of triacylglycerols | |
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| All natural oils are complex mixtures of molecular species | |
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| The storage of triacylglycerols in animals and plants | |
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| Adipose tissue depots are the sites of TAG storage in animals | |
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| Milk triacylglycerols provide a supply of energy for the needs of the new-born | |
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| Some plants use lipids as a fuel, stored as minute globules in the seed | |
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| The biosynthesis of triacylglycerols | |
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| Pathways for complete (de novo) synthesis build-up TAG from small basic components | |
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| The glycerol 3-phosphate pathway in mammalian tissues provides a link between TAG and phospholipid metabolism | |
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| The dihydroxyacetone phosphate pathway in mammalian tissues is a slight variant to the main glycerol 3-phosphate pathway and provides an important route to ether lipids | |
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| Formation of triacylglycerols in plants involves the co-operation of different subcellular compartments | |
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| The monoacylglycerol pathway is important mainly in rebuilding TAG from absorbed dietary fat | |
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| The catabolism of acylglycerols | |
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| The nature and distribution of lipases | |
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| Animal triacylglycerol lipases play a key role in the digestion of food and in the uptake and release of fatty acids by tissues | |
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| Plant lipases break down the lipids stored in seeds in a specialized organelle, the glyoxysome | |
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| The integration and control of animal acylglycerol metabolism | |
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| Fuel economy: the interconversion of different types of fuels is hormonally regulated to maintain blood glucose concentration within the normal range and ensure storage of excess dietary energy in triacylglycerols | |
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| The control of acylglycerol biosynthesis is important, not only for fuel economy but for membrane formation, requiring close integration of storage and structural lipid metabolism | |
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| Mobilization of fatty acids from fat stores is regulated by hormonal balance, which in turn is responsive to nutritional and physiological states | |
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| Wax esters | |
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| Occurrence and characteristics | |
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| Biosynthesis of wax esters involves the condensation of a long-chain fatty alcohol with fatty acyl-CoA | |
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| Digestion and utilization of wax esters is poorly understood | |
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| Surface lipids include not only wax esters but a wide variety of lipid molecules | |
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| Summary | |
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| Further Reading | |
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| Dietary lipids | |
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| Lipids in food | |
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| The fats in foods are derived from the structural and storage fats of animals and plants | |
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| The fatty acid composition of dietary lipids depends on the relative contributions of animal and plant structural or storage lipids | |
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| Industrial processing may influence the chemical and physical properties of dietary fats either beneficially or adversely | |
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| Catalytic hydrogenation | |
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| Heating | |
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| Irradiation | |
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| Interesterification | |
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| Fractionation | |
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| Structured fats | |
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| A few dietary lipids may be toxic | |
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| Cyclopropenes | |
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| Long-chain monoenes | |
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| Trans-unsaturated fatty acids | |
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| Lipid peroxides | |
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| Roles of dietary lipids | |
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| Triacylglycerols provide a major source of metabolic energy especially in affluent countries | |
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| Lipids supply components of organs and tissues for membrane synthesis and other functions | |
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| Foetal growth | |
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| Post-natal growth | |
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| Dietary lipids supply essential fatty acids that are essential to life but cannot be made in the animal body | |
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| Historical background: discovery of essential fatty acid deficiency | |
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| Biochemical basis for EFA deficiency | |
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| Functions of essential fatty acids | |
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| Which fatty acids are essential? | |
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| What are the quantitative requirements for essential fatty acids in the diet? | |
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| Dietary lipids supply fat-soluble vitamins | |
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| Vitamin A | |
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| Vitamin D | |
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| Vitamin E | |
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| Vitamin K | |
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| Lipids play an important role in enhancing the flavour and texture and therefore the palatability of foods | |
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| Odour | |
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| Taste | |
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| Texture | |
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| Dietary lipids in relation to immune function | |
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| Components of the immune system and their functional assessment | |
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| Summary of lipid effects on different components of immunity | |
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| Influence on target cell composition | |
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| Influence on lymphocyte functions ex vivo | |
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| Influence on antibody production | |
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| Influence on delayed-type hypersensitivity | |
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| Graft versus host and host versus graft reactions and organ transplants | |
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| Survival after infection | |
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| Influence on autoimmune and inflammatory disease processes | |
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| Mechanisms | |
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| Membrane properties | |
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| Availability of eicosanoid precursors | |
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| Availability of vitamin E | |
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| Gene expression | |
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| Implications for dietary advice | |
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| Lipids and cancer | |
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| Dietary lipids and cancer | |
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| Cellular lipid changes in cancer | |
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| Lipids and the treatment of cancer | |
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| Summary | |
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| Further Reading | |
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| Lipid transport | |
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| Digestion and absorption | |
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| Intestinal digestion of dietary fats involves breakdown into their component parts by a variety of digestive enzymes | |
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| The intraluminal phase of fat absorption involves passage of digestion products into the absorptive cells of the small intestine | |
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| The intracellular phase of fat absorption involves recombination of absorbed products in the enterocytes and packaging for export into the circulation | |
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| Malassimilation of lipids, through failure to digest or absorb lipids properly, can arise from defects in the gut or other tissues but may also be induced deliberately | |
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| Transport of lipids in the blood: plasma lipoproteins | |
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| Lipoproteins can be conveniently divided into groups according to density | |
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| The apolipoproteins are the protein moieties that help to stabilize the lipid; they also provide specificity and direct the metabolism of the lipoproteins | |
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| The different classes of lipoprotein particles transport mainly triacylglycerols or cholesterol through the plasma | |
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| Specific lipoprotein receptors mediate the cellular removal of lipoproteins and of lipids from the circulation | |
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| Membrane receptors | |
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| The LDL-receptor | |
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| The LDL-receptor-related protein and other members of the LDL-receptor family | |
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| Scavenger receptors | |
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| The lipoprotein particles transport lipids between tissues but they interact and are extensively remodelled in the plasma compartment | |
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| Species differ quantitatively in their lipoprotein profiles | |
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| The co-ordination of lipid metabolism in the body | |
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| The sterol regulatory element binding protein (SREBP) system controls pathways of cholesterol accumulation in cells and may also control fatty acid synthesis | |
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| The peroxisome proliferator activated receptor (PPAR) system regulates fatty acid metabolism in liver and adipose tissue | |
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| Other nuclear receptors are activated by fatty acids and affect gene expression | |
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| Adipose tissue secretes hormones and other factors that may themselves play a role in regulation of fat storage | |
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| Diseases involving changes or defects in lipid metabolism | |
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| Atherosclerosis | |
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| Risk factors for CHD and the effects of diet | |
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| Hyperlipoproteinaemias (elevated circulating lipoprotein concentrations) are often associated with increased incidence of cardiovascular disease | |
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| Obesity and diabetes are associated with increased risk of cardiovascular diseases | |
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| Hypolipoproteinaemias are rare conditions of abnormally low plasma lipoprotein concentrations | |
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| Summary | |
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| Further Reading | |
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| Lipids in cellular structures | |
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| Cell organelles | |
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| Glycerolipids | |
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| Phosphoglycerides are the major lipid components of most biological membranes | |
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| Phosphonolipids constitute a rare class of lipids found in few organisms | |
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| Glycosylglycerides are particularly important components of photosynthetic membranes | |
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| Betaine lipids are important in some organisms | |
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| Ether-linked lipids and their bioactive species | |
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| Sphingolipids | |
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| Sterols | |
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| Major sterols | |
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| Other steroids | |
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| Membrane structure | |
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| Early models already envisaged a bilayer of lipids but were uncertain about the location of the proteins | |
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| The lipid-globular protein mosaic model now represents the best overall picture of membrane structure | |
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| Membrane structure is not static but shows rapid movement of both lipid and protein components | |
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| Further remarks on the lipid composition of membranes | |
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| Transbilayer asymmetry is an essential feature of all known biological membranes | |
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| Lateral heterogeneity is probably important in some membranes at least | |
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| Physical examination of membranes reveals their fluid properties | |
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| General functions of membrane lipids | |
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| Membrane lipids are modified to maintain fluidity at low temperatures | |
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| Lipids and membrane fusion | |
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| Lipids and proteins interact in order to determine membrane structure and shape | |
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| Why are there so many membrane lipids? | |
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| Liposomes and drug delivery systems | |
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| Lipid anchors for proteins | |
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| Acylation | |
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| Prenylation | |
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| GPI-anchors | |
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| Lipids as components of the surface layers of different organisms | |
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| Cutin, suberin and waxes - the surface coverings of plants | |
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| Mycobacteria contain specialized cell-wall lipids | |
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| Lipopolysaccharide forms a major part of the cell envelope of Gram-negative bacteria | |
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| Gram-positive bacteria have a completely different surface structure | |
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| Insect waxes | |
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| Lipids of the skin--the mammalian surface layer and skin diseases | |
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| Summary | |
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| Further Reading | |
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| Metabolism of structural lipids | |
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| Phosphoglyceride biosynthesis | |
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| Tracer studies revolutionized concepts about phospholipids | |
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| Formation of the parent compound, phosphatidate, is demonstrated | |
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| A novel cofactor for phospholipid synthesis was found by accident | |
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| The core reactions of glycerolipid biosynthesis are those of the Kennedy pathway | |
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| The zwitterionic phosphoglycerides can be made using CDP-bases | |
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| CDP-diacylglycerol is an important intermediate for phosphoglyceride formation in all organisms | |
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| Phospholipid formation in E. coli is entirely via CDP-diacylglycerol | |
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| Differences between phosphoglyceride synthesis in different organisms | |
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| Plasmalogen biosynthesis | |
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| Platelet activating factor (PAF): a biologically active phosphoglyceride | |
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| Degradation of phospholipids | |
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| General features of phospholipase reactions | |
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| Phospholipase A activity is used to remove a single fatty acid from intact phospholipids | |
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| Phospholipase B and lysophospholipases | |
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| Phospholipases C and D remove water-soluble moieties | |
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| Phospholipids may also be catabolized by non-specific enzymes | |
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| Metabolism of glycosylglycerides | |
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| Biosynthesis of galactosylglycerides takes place in chloroplast envelopes | |
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| Catabolism of glycosylglycerides | |
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| Relatively little is known of the metabolism of the plant sulpholipid | |
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| Metabolism of sphingolipids | |
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| Biosynthesis of the sphingosine base and ceramide | |
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| Cerebroside biosynthesis | |
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| Formation of neutral glycosphingolipids | |
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| Ganglioside biosynthesis | |
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| Sulphated sphingolipids | |
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| Sphingomyelin is both a sphingolipid and a phospholipid | |
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| Catabolism of the sphingolipids | |
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| Cholesterol biosynthesis | |
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| Acetyl-CoA is the starting material for terpenoid as well as fatty acid synthesis | |
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| Further metabolism generates the isoprene unit | |
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| Higher terpenoids are formed by a series of condensations | |
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| A separate way of forming the isoprene unit occurs in plants | |
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| Sterol synthesis requires cyclization | |
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| Cholesterol is an important metabolic intermediate | |
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| It is important that cholesterol concentrations in plasma and tissues are regulated within certain limits and complex regulatory mechanisms have evolved | |
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| Specific roles | |
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| Pulmonary surfactant | |
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| Lipid storage diseases (lipidoses) | |
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| The 'phosphatidylinositol cycle' in cell signalling | |
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| A wider range of lipid signalling molecules | |
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| Phospholipase D in cell signalling | |
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| Role of sphingolipids in cellular signalling | |
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| Summary | |
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| Further Reading | |
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| Index | |