1、Section K,Lipid Metabolism,K1 Structures and roles of fatty acids,1. Lipid Biological lipids are a chemically diverse group of compounds, the common and defining feature of which is their insolubility in water. Fats and oils (storage lipids) Phospholipids and sterol (major elements of membranes),The

2、 fats and oils used almost universally as stored forms of energy in living organisms are derivatives of fatty acids. Typical type of fatty acid-containing compounds are triacylglycerols.,2. Structure and properties of Fatty acids,3. Nomenclature,Fatty acids are named according to the number of carbo

3、n atoms in the chain and the number and position of any double bonds. Palmitate (C16:0) 棕櫚酸 Stearate (C18:0) 硬脂酸 Oleate (C18:1) 油酸 Linoleate (C18:2) 亞油酸 Linolenate (C18:3) 亞麻酸 Arachidonate (C20:4) 花生四稀酸,Nomenclature of fatty acids,2 systems Omega system: counting the first double bond from the methy

4、l end Delta system: counting the first double bond from the carboxyl end,Structures of some important plant fatty acids,Linoleic acid (LA, 18:2, -6, 9,12) (abundant in vegetable oils) 18 1 CH3 COOH 12 9 -Linolenic acid (ALA, -18:3, -3, 9,12,15) (abundant in linseed (flax) 18 15 12 9 1 CH3 COOH -Lino

5、lenic acid (GLA, -18:3, -6, 6,9,12) (abundant in evening primrose oil) 18 1 CH3 COOH 12 9 6,4. Roles Components of membranes (glycerophospholipids and sphingolipids) Covalently joined with some proteins Energy stores (triacylglycerols) and fuel molecule As hormones and intracellular second messengers (DAG, diacylglycerol),5. Prostaglandins (前列腺素）,前列腺素（PG）實際上是一類具有生物活性的物質(zhì)的總稱，目前已發(fā)現(xiàn)的有幾十種，它的基本結(jié)構(gòu)為含一個環(huán)戊烷及兩個脂肪側(cè)鏈的二十碳脂肪酸，即前列腺烷酸。 由于環(huán)戊烷上的不飽和鍵位置或取代基不同，