1. 10.3 Lipids as Signals, Cofactors, and Pigments

2. Biologically active lipids Active roles of lipids in metabolic traffic 1. Hormones or intracellular messengers 2. Enzyme cofactors - electron-transfer reactions in chloroplasts and mitochondria - sugar-transfer reactions in various glycosylation reactions 3. Pigment molecules - light-capture in vision and photosynthesis - natural colorations 4. Volatile lipids - communication b/t plants - protection or attraction reagents

3. Phosphatidylionsitol and Sphingolipids Intracellular signals Phosphatidylinositol 4,5-bisphosphate

4. Extracellular signals (hormones)  Activation of PLC  Generation of IP 3 & diacyglycerol

5. Phosphatidylionsitol and Sphingolipids Phosphatidylinositol 3,4,5-trisphosphate (PIP 3 ) - Site for formation of signaling complex

6. Phosphatidylionsitol and Sphingolipids Sphingolipids - Ceramide & sphingomyelin; regulators of protein kinase - Ceramide & its derivatives cell division, differentiation, migration, apoptosis

7. Eicosanoids Paracrine hormones  Acting only on cells nearby Aarachidonic acid  20:4(  5,8,11,14 )  Precursors for all eicosanoids

8. Three classes of Eicosanoids Prostaglandin (PG)  PGE : ether-soluble  PGF : phosphate buffer-soluble  Smooth muscle contraction of uterus, blood flow to specific organs, wake-sleep cycle etc.  Regulating the synthesis of cAMP  Mediator of diverse hormones Thromboxanes  Produced by platelets (thrombocytes)  Formation of blood clots, reduction of blood flow to the site of a clot  Nonsteroidal antiinflammatory drugs (NSAIDs)  Aspirin, ibuprofen  Inhibition of prostaglandin H 2 synthase (cyclooxygenase COX) Leukotrienes  Three conjugated double bonds  Contraction of the muscle lining the airways of the lung  Overproduction  Asthma  Anaphylactic shock : by bee stings, penicillin etc.

9. cAMP as a Secondary Messenger

10. Steroid Hormones Oxidized derivatives of sterols  Lacking alkyl chain on ring D of cholesterol  More polar than cholesterol Working mechanism (endocrine)  Moving through blood stream (protein carriers)  Bind to specific receptor in nucleus & regulate gene expression  Very high affinity to the receptor  Working at less than nanomolar conc. Types  Sex hormones  Testosterone (testes)  Estradiol (ovaries, placenta)  Cortisol & aldosterone (adrenal cortex)

11. Steroid Hormones Synthetic steroid drugs : inhibition of arachidonic acid release by phospholipase A 2

12. Lipid-based volatile signals of vascular plants Liphophilic compounds  Volatile substances  Attraction or repellent agent (pollinators, herbivores)  Tools for communication Derivatives of fatty acids or condensation of isoprene units  Jasmonate (jasmine oil), geraniol (geranium),  -pinene (fine tree), limonene (limes), menthol, etc.

13. Vitamin A, D, E, K - Isoprenoid compounds Vitamin A & D; precursors of hormones Vitamin D 3 (cholecalciferol)  Vitamin D 3 formation from UV-driven reaction of 7-dehydrocholesterol  Produced in the skin  in liver, enzymatic conversion to 1,25-dihydroxycholecalciferol  Regulation of gene expression, calcium uptake (the intestine)  Regulation of calcium levels in kidney and bone Deficient disease  Rickets (defective bone formation) Fat-soluble isoprenoid compounds

14. Vitamin A (retinol) - Produced from  -carotene (enzymatic conversion) Hormone : retinoic acid (vit A derivative)  Regulation of gene expression in development of epithelial tissue (skin)  Drug ingredient for acne and wrinkled skin Visual pigment: retinal (vit A derivative)  initiating responses of visual cells in retina Deficiency  Dryness of skins, eyes, mucous membranes Retardation of development and growth, night blindness Fat-soluble isoprenoid compounds

15. Vitamin E (Tocopherols)  Substituted aromatic ring + Long isoprenoid chains  Located in membrane, lipid deposit, lipoprotein  Biological antiboxidants; removal of oxygen radicals (by aromatic ring)  Rich in eggs, vegetable oils, wheat germ Vitamin K  Oxidation/reduction cycle of aromatic ring  involved in the formation of active prothrombin  Deficiency  slow blood clotting Fat-soluble isoprenoid compounds

16. Warfarin  Synthetic compound  Inhibition of active prothrombin formation  blocking rapid blood clotting Ubiquinone (coenzyme Q) & plastoquinone  Liphophilic electron carriers in mitochondria & chloroplast  ATP synthesis Fat-soluble isoprenoid compounds

17. Dolichols  Activation of sugar precursors for biosynthesis  Assembly of carbohydrates of bacterial cell wall  Addition of polysaccaride for glycoproteins and glycolipids Fat-soluble isoprenoid compounds