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

Fatty Acids Carboxylic Acid at C1 Acyl chain –Usually 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

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

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

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

Phospholipases 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 A1

Plasmalogens Have an  unsaturated ether in place of the ester at C1 in a glycerophospholipid Most common head groups are phosphoserine, phosphocholine and phosphoethanolamine

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

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

Steroids Cholesterol stiffens membranes –can be fatty acylated Steroid hormones are lipid soluble –Receptors are cytoplasmic

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 Ca 2+ metabolism esp bone growth and repair

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

Arachidonic Acid Metabolites ProstaglandinH2 is a precursor to –Prostaglandins –Prostacyclins –Thromboxanes PGH 2 synthase inibited by aspirin, acetominophen and ibuprophen PGH 2 synthase