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12. lípidos
- 1. 12. Lípidos
- 2. Características Insolubilidad en agua Almacenamiento de energía (grasas y aceites) Elementos estructurales de las membranas biológicas Cofactores Transportadores de e- Pigmentos Anclaje hidrofóbico para proteínas Chaperonas en el folding de proteínas Agentes emulsificantes en el tracto digestivo Hormonas Mensajeros intracelulares
- 4. Insaponificables Simples C, H, O Grasas Aceites Acilglicéridos Céridos Ceras Fosfolípidos Fosfoglicéridos Fosfoesfingolípidos Glucolípidos Cerebrosidos Gangliósidos Terpenoides Esteroides Eicosanoides Saponificables Complejos N, P, S, biomól.
- 5. Simples
- 10. Reacción de esterificación Reacción de saponificación
- 12. Complejos
- 18. Lípidos-éter
- 24. Asociados
- 25. Mentol, el geraniol, moneno,alcanfor, eucaliptol, vainillina. Vitaminas, como la vit.A, vit. E, vit.K. Pigmentos vegetales: carotina y xantofila. Isopreno
- 26. Terpenos
- 27. Esterano
- 31. Sales Biliares
- 32. (NSAIDs): Nonsteroidal antiinflammatory drugs Cyclooxygenase (prostaglandin H2 synthase).
Notas del editor
- In general, glycerophospholipids contain a C16 or C18 saturated fatty acid at C-1 and a C18 to C20 unsaturated fatty acid at C-2. With few exceptions, the biological significance of the variation in fatty acids and head groups is not yet understood.
- Galactolipids are localized in the thylakoid membranes (internal membranes) of chloroplasts; they make up 70% to 80% of the total membrane lipids of a vascular plant. They are probably the mostabundant membrane lipids in the biosphere. Phosphate is often the limiting plant nutrient in soil, and perhaps the evolutionary pressure to conserve phosphate for more critical roles favored plants that made phosphatefree lipids. Plant membranes also contain sulfolipids, in which a sulfonated glucose residue is joined to a diacylglycerolin glycosidic linkage. In sulfolipids, the sulfonate on the head group bears a fixed negative chargelike that of the phosphate group in phospholipids
- They contain no glycerol. Sphingolipids are composed of one molecule of the long-chain amino alcohol sphingosine (also called 4-sphingenine) or one of its derivatives, one molecule of a long-chain fatty acid, and a polar head group that is joined by a glycosidic linkage in some cases and by a phosphodiester in others
- Sterols are structural lipids present in the membranesof most eukaryotic cells. The characteristic structure ofthis fifth group of membrane lipids is the steroid nucleus, consisting of four fused rings, three with six carbonsand one with five. The steroid nucleusis almost planar and is relatively rigid; the fused ringsdo not allow rotation about C-C bonds.Cholesterol. The stick structure of cholesterol is visiblethrough a transparent surface contour model of the molecule (fromcoordinates supplied by Dave Woodcock). In the chemical structure,the rings are labeled A through D to simplify reference to derivativesof the steroid nucleus, and the carbon atoms are numbered in blue.The C-3 hydroxyl group (pink in both representations) is the polar headgroup. For storage and transport of the sterol, this hydroxyl group condenseswith a fatty acid to form a sterol ester.
- Sterols are structural lipids present in the membranesof most eukaryotic cells. The characteristic structure ofthis fifth group of membrane lipids is the steroid nucleus, consisting of four fused rings, three with six carbonsand one with five. The steroid nucleusis almost planar and is relatively rigid; the fused ringsdo not allow rotation about C-C bonds.Cholesterol. The stick structure of cholesterol is visiblethrough a transparent surface contour model of the molecule (fromcoordinates supplied by Dave Woodcock). In the chemical structure,the rings are labeled A through D to simplify reference to derivativesof the steroid nucleus, and the carbon atoms are numbered in blue.The C-3 hydroxyl group (pink in both representations) is the polar headgroup. For storage and transport of the sterol, this hydroxyl group condenseswith a fatty acid to form a sterol ester.
- Arachidonic acid and some eicosanoid derivatives.(a) In response to hormonal signals, phospholipaseA2 cleaves arachidonic acid–containing membrane phospholipids torelease arachidonic acid (arachidonate at pH 7), the precursor to variouseicosanoids. (b) These compounds include prostaglandins suchas PGE1, in which C-8 and C-12 of arachidonate are joined to formthe characteristic five-membered ring. In thromboxane A2, the C-8 andC-12 are joined and an oxygen atom is added to form the sixmemberedring. Leukotriene A4 has a series of three conjugated doublebonds. Nonsteroidalantiinflammatory drugs (NSAIDs) such asaspirin and ibuprofen block the formation of prostaglandins and thromboxanesfrom arachidonate by inhibiting the enzyme cyclooxygenase(prostaglandin H2 synthase).They are known to be involved in reproductivefunction; in the inflammation, fever, and painassociated with injury or disease; in the formation ofblood clots and the regulation of blood pressure; in gastricacid secretion; and in a variety of other processesimportant in human health or disease.All eicosanoids are derived from arachidonic acid(20:4(5,8,11,14)) (Fig. 10–18), the 20-carbon polyunsaturatedfatty acid from which they take their general name (Greek eikosi, “twenty”). There are threeclasses of eicosanoids: prostaglandins, thromboxanes,and leukotrienes.