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Biological Lipids and Bilayers

Biological Lipids and Bilayers. Lipids are nearly insoluble in Water Form Biological membranes Regulate solute flow and signalling Provide concentrated energy stores Structure, Classification and Nomenclature Fatty acids, polar headgroups, steroids and eicosanoids Lipid Bilayers

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Biological Lipids and Bilayers

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  1. Biological Lipids and Bilayers • Lipids are nearly insoluble in Water • Form Biological membranes • Regulate solute flow and signalling • Provide concentrated energy stores • Structure, Classification and Nomenclature • Fatty acids, polar headgroups, steroids and eicosanoids • Lipid Bilayers • Micelles, bilayers and vesicles • Fluidity

  2. Fatty Acids • Carboxylic Acid at C1 • Acyl chain • Usually 14 - 20 carbons (including C1) • Usually even # -- built from C2 (acetyl) units • Saturated (no double bonds) • Strong interactions between parallel acyl chains High MP. • UnSaturated (double bonds) • Almost always cis, Often at C9 • Weak interactions between parallel acyl chains Low MP. • Polyunsaturated • Usually not conjugated

  3. Triacylglycerols • Storage form of fatty acids • Charges neutralized • Fatty acids added or removed one at a time

  4. Glycerophospholipids • The simplest Glycerophospholipid is phosphatidic acid • 1, 2 diacyl glycerol with a phosphate on C3 • Phosphatidyl ethanolamine bears a phospho ethanolamine at C3 • Similarly phosphatidyl • Choline • Serine • Inositol

  5. Cardiolipipins • Phosphatidyl glycerol contains a second glycerol head group • Cardiolipins have 2 glycerols connected by a single phosphate and 4 acyl chains

  6. Phospholipases • A1 • Cleave ester linkages in phospholipids • Phospholipase A1 • fatty acyl chain 1 • Phospholipase A2 • fatty acyl chain 2 • Phospholipase C • Glycerol - phosphate • Phospholipase D • Phosphate - inositol

  7. Plasmalogens • Have an a, b unsaturated ether in place of the ester at C1 in a glycerophospholipid • Most common head groups are phosphoserine , phosphocholine and phosphoethanolamine

  8. Sphingolipids • Sphingosine is an 18 Carbon amino alcohol • Ceramides are N-Acyl fatty acid derivatives of sphingosine • Sphingomyelins are sphingophospholipids that bear phosphoethanolamine or phosphocholine head groups

  9. GlycoSphingolipids • Carbohydrates linked via simple ester linkage to the primary alcohol of ceramide • Glycosphingolipids are extracellular • Concentrated in Neural membranes • Cerebrosides have 1 sugar • Usually glucose or mannose • Gangliosides • have oligosaccharides

  10. Steroids • Cholesterol stiffens membranes • can be fatty acylated • Steroid hormones are lipid soluble • Receptors are cytoplasmic

  11. Steroid Hormones • Glucocorticoids • Regulate metabolism and inflammation • Mineralocorticoids • Regulate Salt and Osmotic balance in Kidney • Androgens - Male hormones • Estrogens - Female hormones • Vitamin D derivatives • UV light can cleave C9-C10 • Regulates Ca2+ metabolism esp bone growth and repair

  12. Eicosanoids • C20 Fatty acids • membrane localized, short term signalling molecules • Precursor is arachidonic acid • 5,8,11,14, Eicosatetraeneoic acid • Prostaglandins • Pain and fever • Prostacyclins • Stimulate vasodilation, free flow of blood • Thromboxanes • Stimulate vasoconstriction, clotting • Leukotrienes • Inflammation, asthma

  13. Arachidonic Acid Metabolites • ProstaglandinH2 is a precursor to • Prostaglandins • Prostacyclins • Thromboxanes • PGH2 synthase inibited by aspirin, acetominophen and ibuprophen PGH2 synthase

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