FATTY ACIDS Valdost State University脂肪酸瓦尔多斯塔州立大学.docVIP

LIPIDS Distinguishing characteristics: insoluble in water either non-polar or amphipathic Some functions of lipids energy storage (adipose tissue) cell membranes hormones, vitamins and their precursors insulation buoyancy protection (e.g. oil on duck feathers) structural like beeswax neural tissues cell recognition many others Major Classes of Lipids (may be divided differently in other sources) Triacylglycerols (triglycerides, storage lipids, simple lipids, neutral fats, etc.) Phospholipids Sphingolipids (some of these are also classified as phospholipids or glycolipids) Archaebacterial ether lipids Steroids FATTY ACIDS - precursors of simple lipids, phospholipids and sphingolipids General Structure See the table 10-1 on page 344 for common fatty acids. Hydrocarbon tails vary in the amount of saturation. Saturated hydrocarbons Alkanes - all single carbon-carbon bonds Unsaturated hydrocarbons Alkenes - one or more double bonds Alkynes - one or more triple bonds Hydrogenation of alkenes (reverse is dehydrogenation of alkanes) Melting points - depend on degree of saturation Double bonds introduce kinks (unsaturation) Kinks make packing into solids (or semisolids) more difficult Result - The more highly unsaturated the lower the melting point(It needs to be cooled more to get it to solidify.) Compare: Corn oil - liquid at room temperature Margarine from corn oil - solid at room temperature melts between room and body temperatures Which is more saturated, oil or margarine? ______ Many foods have dehydrogenated vegetable oil or hydrogenated vegetable oil Amount of saturation/unsaturation can be varied to give desired properties. Symbols for Fatty Acid Carbon Skeletons N : M ((x,y,z,...) N = number of carbons in the chain M = number of carbon-carbon double bonds x,y,z,... = locations of double bonds by carbon number Carbon numbers - Carboxylate carbon is number 1 Chain carbons are numbered away from this. Last carbon is also referred to as