Chapter 19 Lipids (类脂) Ref: Wade, chapter 25

Lipids are compounds that can be extracted from cells and tissues by nonpolar organic solvents. Waxes: 蜡 Complex lipids Fats and oils 油脂: glycerides phospholipides: 磷脂 Steriods 甾体 Simple lipids Terpenes 萜 Prostaglandins 前列腺素

19-1 Waxes Most waxes are esters of long-chain fatty acids and long-chain alcohols. Waxes are found as protective coatings on the skin, fur, or feathers of animals, and on the leaves and fruits of plants. spermaceti 鲸蜡 beeswax 蜂蜡的一种 Notice: parafin wax (石蜡) is a mixture of alkanes with high molecular weight。

19-2 Triglycerides 三酸甘油酯 （25-3, 4） Oils: Triacylglycerols that are liquids at room temperature. Fats: Triacylglycerols that are solids at room temperature. The primary function of triacylglycerols in animal is as an energy reserve.

Common naturally occurring fatty acids 月桂酸 肉豆蔻酸 软脂酸 硬脂酸 花生酸

棕榈油酸 油酸 亚油酸 亚麻酸 花生四烯酸

A fat An oil

① Most of fatty acids have unbrached chains and they have an even number of carbon atoms. ② The double bonds in unsaturated fatty acids are all cis and not conjugated.. ③ Saturated fatty acids have relatively high melting points and unsaturated fatty acids have relatively low points. Saponification reaction: soaps Synthetic detergents

Synthesis of detergents offer an advantage over soaps; they function well in “hard” water.

19-3 Phospholipids 磷脂 （25-5） a phosphatidic acid 磷脂酸 hydrophobic portion hydrophilic portion

Phosphoacylglycerols form membranes by arranging themselves into a lipid bilayer

19-4 Terpenes 萜类 Terpenes contain carbon atoms in multiples of five They are made by joining together 5-carbon isoprene units The Isoprene Rule 异戊二烯规则

Classification of terpenes 单萜 三萜 倍半萜 四萜 双萜 monoterpenes

triterpenes squalene 角鲨烯

Lycopene (番茄红素) b-carotene（胡萝卜素） tetraterpenes

Vitamin A

The biosynthesis of terpenes:

19-5 Steroids (甾体)

The A and B rings are also trans fused in most naturally occurring steroids Substituents on the same side of the steroid ring system as the angular methyl groups are b-substituents Those on the opposite side of the plane of the ring system are a-substituents

Cholesterol 胆固醇 Cholesterol is known to serve as an intermediate in the biosynthesis of all of the steroids of the body.

Biosynthesis of Cholesterol 角鲨烯 （三萜） 羊毛甾醇 羊毛甾醇 （三萜） 胆固醇

conrotatory 顺旋 7-脱氢胆甾醇 [1,7] σ-迁移

19-6 Prostaglandins 前列腺素 Structure: C20-carboxylic acids a five-membered ring, at least one double bond, several oxygen-Containing functional groups.

The biosynthesis of prostaglandins of the 2 series begins with a C20 polyenoic acid, arachidonic acid.