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Lipids

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  1. Lipids Lipids of Physiologic Significance

  2. BIOMEDICAL IMPORTANCE • The lipids • The common property • insoluble in water • soluble in nonpolarsolvents • They are important dietary constituents • high energy value • fat-soluble vitamins • essential fatty acids • Fat is stored in adipose tissue

  3. BIOMEDICAL IMPORTANCE • Thermal insulator • electrical insulators • cellular constituents • Membranes • Transport • Lipoproteins • Lipid biochemistry is necessary • obesity, diabetes mellitus, atherosclerosis, polyunsaturated fatty acids in nutrition and health

  4. Classification • Simple lipids • Esters of fatty acids with various alcohols • Complex lipids • groups in addition to an alcohol and a fatty acid • Phospholipids • Glycerophospholipids • Sphingophospholipids • Glycolipids • Other complex lipids • Sulfolipids and aminolipids • Lipoproteins

  5. Classification • Precursor and derived lipids • Neutral lipids • acylglycerols (glycerides),cholesterol, and cholesteryl esters

  6. Free fatty • Free fatty acids • Saturated • -anoic • Unsaturated • -enoic • 1,2,3,… • α, β, γ ,… ω or n carbons • Δ

  7. Saturated fatty acids

  8. Unsaturated Fatty Acids • Monounsaturated • Polyunsaturated • Eicosanoids • eicosa- (20-carbon) polyenoic fatty acids • Prostanoids • Prostaglandins(PGs) • Prostacyclins (PGIs) • Thromboxanes (TXs) • Leukotrienes (LTs) • Lipoxins (LXs)

  9. Prostaglandins • The number of double bonds • PG1, PG2, PG3 • Different substituent groups (on ring) • A, B,C,etc

  10. The leukotrienes andlipoxins • Lipoxygenase pathway • three or four conjugated double bonds • Leukotrienes cause bronchoconstriction as well as being potent proinflammatoryagents and play a part in asthma

  11. Unsaturated Fatty Acids • Geometric isomerism • Cis • on the same side • Trans • if on opposite sides • as a by-product of the saturation of fatty acids • ingestion of ruminant fat • Significance • Molecular packing in membranes

  12. Unsaturated fatty acids of physiologic and nutritional significance

  13. Structure of some unsaturated fatty acids

  14. Physical and Physiologic Propertiesof Fatty Acids • Chain Length and Degree of Unsaturation • even-numbered-carbon fatty acids • The melting points

  15. TRIACYLGLYCEROLS (TRIGLYCERIDES) • THE MAIN STORAGE FORMS OF FATTY ACIDS • Mono- and diacylglycerols

  16. PHOSPHOLIPIDS • MAIN LIPID CONSTITUENTS OF MEMBRANES • derivatives of phosphatidic acid • Phosphatidylcholines (Lecithins) • the most abundant phospholipids of the cell membrane • represent a large proportion of the body’s store of choline

  17. PHOSPHOLIPIDS • Surfactant • Dipalmitoyl lecithin • respiratory distress syndrome • Phosphatidylethanolamine (cephalin) • Phosphatidylserine • Phosphatidylinositol • Cardiolipin

  18. Lysophospholipids

  19. Phospholipids • Plasmalogens

  20. Sphingomyelins

  21. GLYCOLIPIDS • GLYCOSPHINGOLIPIDS • NERVE TISSUES • CELL MEMBRANE • Galactosylceramide • Sulfatide • Sulfogalactosylceramide • Glucosylceramide • Glycosphingolipid of extraneural tissues

  22. Simple glycosphingolipids • Complex glycosphingolipids • Gangliosides • Sialic acid • The simplest ganglioside found in tissues is GM3 • Functions • Receptor, …

  23. STEROIDS • Cholesterol • Atherosclerosis • As Precursor • Sterol • Has one or more hydroxylgroups and no carbonyl orcarboxyl groups

  24. Stereoisomers • “Chair” or a “boat” form • The rings can be either cis or trans • β bonds • above the plane of the rings • α bonds • bonds attaching groups below

  25. an all-trans configuration between adjacent rings

  26. a cis configuration between rings A and B

  27. Cholesterol • Cholesteryl ester

  28. Ergosterol • Precursor of Vitamin D

  29. Polyprenoids • Synthesized from five-carbon isoprene units • Include • Ubiquinone • Dolichol • Vitamins • A, D, E, and K, and β-carotene (provitamin A)

  30. LIPID PEROXIDATION • A SOURCE OF FREE RADICALS • Lipids exposed to oxygen • deterioration of foods (rancidity) • damage to tissues • Cancer, inflammatory diseases, atherosclerosis, and aging • Peroxide formation from fatty acids containing methylene-interrupted double bonds • Antioxidants • Vitamin E, Beta-carotene • Urate and vitamin C

  31. AMPHIPATHIC LIPIDS • Form • Membranes, Micelles, Liposomes, & Emulsions • Contain polar groups • Fatty acids, phospholipids, sphingolipids, bile salts, and, to a lesser extent, cholesterol • Part of the molecule is hydrophobic, and part is hydrophilic

  32. Micelles • When a critical concentration of these lipids is present in an aqueous medium • Facilitating absorption of lipids • Liposomes • Formed by sonicating an amphipathic lipid in an aqueous medium • as carriers of drugs

  33. Emulsions • Much larger particles

  34. Waxes • Serve as • Energy Stores and Water Repellents • Esters of long-chain (C14 to C36) saturated and unsaturated fatty acids with long-chain (C16 to C30) alcohols • Their melting points (60 to 100 °C) are generally higher than those of triacylglycerols

  35. Triacontanoylpalmitate, the major component of beeswax

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