1 / 54

Lipids

Lipids. What are Lipids?. Class of biomolecules that are all water insoluble No defining characteristic except that all of them share the same trait: non-polar Most common are fatty acids and esters of fatty acids Functions Energy Storage Cell membrane Thermal blanket and cushion

hedya
Download Presentation

Lipids

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lipids

  2. What are Lipids? • Class of biomolecules that are all water insoluble • No defining characteristic except that all of them share the same trait: non-polar • Most common are fatty acids and esters of fatty acids • Functions • Energy Storage • Cell membrane • Thermal blanket and cushion • Precursors of hormones

  3. Fatty Acids • Fatty acids consist of a hydrocarbon chain with a carboxylic acid at one end. • A 16-C fatty acid: CH3(CH2)14-COO- Non-polarpolar • General Structure:

  4. Fatty Acids • Double bonds in fatty acids usually have the cis configuration. • Most naturally occurring fatty acids have an even number of carbon atoms. • IUPAC naming: • COOH carbon as C1 • Farthest carbon is ω • Total carbons/# double bonds/Δdoublebond position

  5. Fatty Acids • Some fatty acids and their common names: • 14:0myristic acid; 16:0 palmitic acid; 18:0 stearic acid; • 18:1 cisD9  oleic acid • 18:2 cisD9,12  linoleic acid • 18:3 cisD9,12,15a-linonenic acid • 20:4 cisD5,8,11,14arachidonic acid • 20:5 cisD5,8,11,14,17eicosapentaenoic acid (an omega-3) • Essential fatty acids • ALA- ω-3 FA precursor for EPA and DHA • LA – ω-6 FA precursor of AA

  6. Fatty Acid Chemistry • Peroxidation • a non-enzymatic reaction catalyzed by oxygen • may occur in tissues or in foods (spoilage) • the hydroperoxide formed is very reactive and leads to the formation of free radicals which oxidize protein and/or DNA (causes aging and cancer) • principle is also used in drying oils (linseed, tung, walnut) to form hard films

  7. Drying Oils: Application of Peroxidation • based on the ease of autoxidation and polymerization of oils (important in paints and varnishes) • the more unsaturation in the oil, the more likely the “drying” process • Non-drying oils: • Castor, olive, peanut, rapeseed oils • Semi-drying oils • Corn, sesame, cottonseed oils • Drying oils • Soybean, sunflower, hemp, linseed, tung, oiticica oils

  8. Fatty Acid Chemistry • Transesterification • Acid-catalyzed exchange betweein R groups of esters • Frequently-used in polyester, methanolysis and biodiesel industries

  9. Fatty Acid Chemistry • Hydrogenation • Reduces double bonds on unsaturated fatty acids • Prevents oils from going rancid

  10. Fatty Acid Chemistry • Saponification • Base hydrolysis of triglycerides to produce fatty acid salts • High saponification number, shorter chain length

  11. Soaps • Types of soaps: • Sodium soap – ordinary hard soap • Potassium soap – soft soap (shaving soaps are potassium soaps of coconut and palm oils) • Castile soap – sodium soap of olive oil • Green soap – mixture of sodium and potassium linseed oil • Transparent soap – contains sucrose • Floating soap – contains air • Calcium and magnesium soaps are very poorly water soluble (hard water contains calcium and magnesium salts –these insolubilize soaps)

  12. Fatty Acid Chemistry • Iodine Number • measures the degree of unsaturation in a given amount of fat or oil • the iodine number is the number of grams of iodine absorbed by 100 grams of fat • Cottonseed oil: 103 –111 • Olive oil: 79 – 88 • Linseed oil: 175 –202 • frequently used to determine adulteration of commercial lots of oils

  13. Fatty Acid Chemistry • Acetyl Number • the number of milligrams of KOH needed to neutralize the acetic acid of 1 g of acetylated fat

  14. Fatty Acid Chemistry • Reichert-Meisl Number • measures the amount of volatile fatty acids (low MW and water soluble Fas) • the R-M number is the number of milliliters of 0.1N alkali required to neutralize the soluble fatty acids distilled from 5 Gm of fat • butter fat has a high R-M number • Indicator of non-fat compounds in edible fats, or volatile fatty acids

  15. Fats and Oils • fats are solids or semi solids • oils are liquids • melting points and boiling points are not usually sharp (most fats/oils are mixtures) • when shaken with water, oils tend to emulsify • pure fats and oils are colorless and odorless (color and odor is always a result of contaminants) – i.e. butter (bacteria give flavor, carotene gives color)

  16. Waxes • simple esters of fatty acids (usually saturated with long chain monohydric alcohols) • Beeswax – also includes some free alcohol and fatty acids • Spermaceti – contains cetylpalmitate (from whale oil) –useful for pharmaceuticals (creams/ointments; tableting and granulation) • Carnauba wax – from a palm tree from brazil – a hard wax used on cars and boats

  17. Spermaceti source Carnauba wax source Bee’s wax

  18. Glycerides • Function • Storage of energy • Cushions

  19. Triglycerides • Esters of fatty acids and glycerol • Constituent of fats and oils

  20. Phosphoglycerides • aka glycerophospholipids • Major constituent of cell membranes • Structure • Glycerol backbone with esterifies fatty acids at C1 and C2 • Fatty acids are usually non-identical • Phosphate group attached to C1 • A polar group is usually esterified to Pi (usually serine, choline, ethanolamine, glycerol, or inositol

  21. Phosphoglycerides • Structure=Function • Polar region – glycerol, phosphate group, X • Nonpolar region – fatty acid • Amphiphatic character • Ideal for forming bilayers

  22. Phosphoglyceride

  23. Phosphatidyl inositol • Inositol as a polar head group • Has roles in cell signaling as well as a cell membrane component

  24. Ether glycerophospholipids • Possess an ether linkage instead of an acyl group at the C-1 position of glycerol • PAF ( platelet activating factor) - a potent mediator in inflammation, allergic response and in shock (also responsible for asthma-like symptom • The ether linkage is stable in either acid or base • Plasmalogens: cisa,b-unsaturated ethers • The alpha/beta unsaturated ether can be hydrolyzed more easily

  25. Sphingolipids • derivatives of the lipid sphingosine, which has a long hydrocarbon tail, and a polar domain that includes an amino group • Like phosphoglycerides, are also constituents of cell membranes • Can be reversibly phosphorylated and utilized as signaling molecule

  26. Sphingolipid Derivatives • Ceramide- amino group of sphingosineforms an amide bond with a fatty acid carboxyl • Sphingomyelinhas a phosphocholine or phosphethanolamine head group. • common constituent of plasma membranes • similar in size and shape to the glycerophospholipidphosphatidyl choline

  27. Sphingolipid Derivatives • Cerebrosidea sphingolipid (ceramide) with a monosaccharide such as glucose or galactose as polar head group. • Ganglioside– a ceramide with polar head group that is a complex oligosaccharide, including the acidic sugar derivative sialicacid • Both are collectively known as glycosphingolipidsand are commonly found on the outer leaflet of the cell membrane

  28. Ganglioside Structure

  29. Ganglioside • Cerebrosides • One sugar molecule • Galactocerebroside – in neuronal membranes • Glucocerebrosides – elsewhere in the body • Sulfatides or sulfogalactocerebrosides • A sulfuric acid ester of galactocerebroside • Globosides: ceramide oligosaccharides • Lactosylceramide • 2 sugars ( eg. lactose) • Gangliosides • Have a more complex oligosaccharide attached • Biological functions: cell-cell recognition; receptors for hormones

  30. Cardiolipids • A polyglycerol phospholipid; makes up 15% of total lipid-phosphorus content of the myocardium – associated with the cell membrane • Cardiolipids are antigenic and as such are used in serologic test for syphilis (Wasserman test)

  31. Sulfolipids • also called sulfatides or cerebroside sulfates • contained in brain lipids • sulfate esters of cerebrosides • present in low levels in liver, lung, kidney, spleen, skeletal muscle and heart • function is not established

  32. Lipid Storage Diseases

  33. Lipid Storage Diease • a group of inherited metabolic disorders in which harmful amounts of fatty materials (lipids) accumulate in various tissues and cells in the body • also known as sphingolipidoses • genetically acquired • due to the deficiency or absence of a catabolic enzyme • Tay Sachs disease • Gaucher’s disease • Niemann-Pick disease • Fabry’s disease

  34. Tay Sachs Disease

  35. Fabry’s Disease

  36. Niemann Pick Disease

  37. Cholesterol and related compounds

  38. Cholesterol • an important constituent of cell membranes, has a rigid ring system and a short branched hydrocarbon tail. • serves as a component of membranes of cells (increases or moderates membrane fluidity) • precursor to steroid hormones and bile acids • storage and transport –cholesterol esters • Cholesterol is largely hydrophobic. • But it has one polar group, a hydroxyl, making it amphipathic.

  39. Steroid Ring System

  40. Eicosanoids • Includes prostaglandins and related compounds • Derivatives of arachidonic acid • Serves as local hormones and intercellular signaling • Key hormones in inflammation response

  41. Eicosanoids • Types of Eicosanoids • Prostaglandins • Prostacyclins • Thromboxanes • Leukotrienes • epoxyeicosatrienoicacids. • Biological Functions • Inflammation • Fever • regulation of blood pressure • blood clotting • immune system modulation • control of reproductive processes and tissue growth • regulation of the sleep/wake cycle

  42. Terpenes • simple lipids, but lack fatty acid component • formed by the combination of 2 or more molecules of 2-methyl-1,3-butadiene (isoprene) • monoterpene (C-10) – made up of 2 isoprene units • sesquiterpene (C-15) – made up of 3 isoprene units • diterpene (C-20) – made up of 4 isoprene units

  43. Terpenes • tetraterpenes (C-40) are not as common as mono, di, and triterpenes • include the carotenoids such as beta-carotene (precursor of vitamin A) and lycopene found in tomatoes • usually colorful compounds due to highly conjugated system • polyisoprenoids or polyprenols consist of numerous isoprene adducts (8 – 22) • examples include dolichol phosphate, undecaprenyl alcohol (bactoprenol) and the side chains of vitamins K, vitamin E and coenzyme Q

  44. Lipid-linked proteins and Lipoproteins

  45. Lipid-linked proteins • Proteins that have lipids covalently bonded to them • Usually found in cell membranes • 3 types are most common: • Prenylated proteins • Farnesylated proteins (C15 isoprene unit) • Geranylgeranylated proteins (C20 isoprene unit) • Fatty acylated proteins • Myristoylated proteins (C14) • Palmitoylated proteins (C16) • glycosylphosphatidylinositol-linked proteins (GPI-linked proteins) • occur in all eukaryotes, but are particularly abundant in parasitic protozoa • located only on the exterior surface of the plasma membrane

  46. Fatty acylatedproteins

  47. Prenylatedproteins

More Related