Lesson 9 Lipids1.Lipids are a family of naturally occurring compounds grouped together on the basisof their relative insolubility in water and solubility in nonpolar solvents.脂质是一类天然化合物家族，其在水中具有不溶解性和在非极性溶剂里具有溶解性。
2.These are naturally occurring molecules that can be isolated from cells and tissuesby extraction using nonpolar organic solvents. 这些天然存在的分子可以通过采用非极性有机溶剂抽屉的方法，在细胞和组织中分离得到。
3.There are two classes of lipids: i) those with ester linkage s that can be hydrolyzed,for example, fats and waxes; ii) those without ester linkages and so cannot by hydrolyzed, for example, cholesterol and steroid s. 脂质分为两类：酯键可以水解的，例如，脂肪和蜡; 没有酯键即不能水解的，例如，胆固醇和类固醇。
4.Fats and oils are triacylglycerols. 脂肪和油脂都是三酰甘油。
5.They are triesters of glycerol (probane-1,2,3-triol) with three long chaincarboxylic acids. 它们是甘油用三个长链羧酸连接成三个酯健。
6.Reaction with aqueous sodium hydroxide yields glycerol and the three fatty acids.用氢氧化钠水解后可产生甘油和三个脂肪酸。
7.Fatty acids are usually unbranched and contain an even number of carbon atoms,usually from 12 to 20. 脂肪酸通常是没有分枝的，包含12 到20个碳原子。
8.If there are any double bonds, they tend to have cis geometry. 如果存在双键，它们趋向存在顺异构体。
9.Fats containing one double bond are monounsaturated and those with more thanone double bond are polyunsaturated. 含有一个双键的脂肪是单不饱和脂肪酸，含多个双键结构的是多不饱和脂肪酸。
10.Saturated fats have a uniform shape that allows them to pack together in a crystallattice. 饱和脂肪酸具有一个相同的形式，可以包裹在一个晶体结构中。
11.Unsaturated fats have double bonds that introduce kinks into the hydrocarbonchain making crystal formation more difficult. 不饱和脂肪酸具有双键，将双键裹到(碳氢化合物)烃链晶体形式里难度更大。
12.This is why saturated fats have higher melting points and are solids at roomtemperature compared to unsaturated fats that tend to be liquids (oils). 这就是为什么饱和脂肪熔点更高, 在室温下是固体,相对而言不饱和脂肪在室温下是液体。
13.The most abundant lipid in olive oil is glyceryl trioleate, a triester formed fromglycerol and oleic acid, a mono-unsaturated fatty acid with a cis double bond in the middle of the C18 chain. 橄榄油有丰富的三油酸甘油酯, 由甘油和油酸，单不饱和脂肪酸形成三酯，其中单不饱和脂肪酸的C18链中间有一个顺式双键。
14.Waxes are mixtures of esters of long chain carboxylic acids and long chainalcohols. 蜡是长链羧酸和长链醇的酯质类混合物。
15.The carboxylic acids usually have an even number of carbon atoms, ranging from16 to 36, and the long chain alcohols also have an even number of carbon atoms,ranging from 24 to 36. 这种羧酸通常有16至36个碳原子，长链醇也含24至36个碳原子。
Fats and Oils脂肪和油脂1.The triesters of fatty acids with glycerol (1,2,3-trihydroxypropane) compose theclass of lipids known as fats and oils. 脂肪酸和甘油三酯组成的类脂类被称为脂肪和油。
2.These triglycerides (or triacylglycerols) are found in both plants and animals, andcompose one of the major food groups of our diet. 这些甘油三酯类（或叫三酰基甘油）存在植物和动物中，构成了我们食物里的主要成分。
3.Triglycerides that are solid or semisolid at room temperature are classified as fats,and occur predominantly in animals. 这些甘油三酸酯在室温下如果是固体或半固体就被分类叫脂肪，一般主要存在动物体内。
4.Those triglycerides that are liquid are called oils and originate chiefly in plants,although triglycerides from fish are also largely oils. 那些液体状的甘油三酯被称为油，主要来源于植物,虽然鱼体内的甘油三酯也大多是油。
Fatty Acids脂肪酸1.The common feature of these lipids is that they are all esters of moderate to longchain fatty acids. 这种脂类的共同特点是所有都是相对于长链脂肪酸的中等酯类。
2.Acid or base-catalyzed hydrolysis yields the component fatty acid, some examplesof which are given in the following table, together with the alcohol component of the lipid. 酸或碱催化水解产生脂肪酸成分和醇类，其中一些例子列在下面的表中。
3.These long-chain carboxylic acids are generally referred to by their common names,which in most cases reflect their sources. 这些长链羧酸一般的命名原则能反映出其来源。
4.Natural fatty acids may be saturated or unsaturated, and as the following dataindicate, the saturated acids have higher melting points than unsaturated acids of corresponding size. 天然的脂肪酸可以饱和的或者不饱和的，并且下面资料表明，饱和脂肪酸与相同大小的不饱和酸比较，熔点的更高。
5.The double bonds in the unsaturated compounds listed on the right are all cis (orZ). 不饱和的脂肪酸里的双键列在右边，全是顺式结构（或Z结构）。
6.The higher melting points of the saturated fatty acids reflect the uniform rod-likeshape of their molecules. 高熔点的饱和脂肪酸的分子表现为棒状的相同结构。
7.The cis-double bond(s) in the unsaturated fatty acids introduce a kink in their shape,which makes it more difficut to pack their molecules together in a stable repeating array or crystalline lattice. 不饱和脂肪酸里顺式双键有一个扭结的结构，使这些分子一起被包裹到一种稳定的重复结构或晶体格子里难度更大些。
8.The trans-double bond isomer of oleic acid, known as elaidic acid, has a linearshape and a melting point of 45 ºC (32 ºC higher than its cis isomer). 油酸的反式双键异构体，即众所周知的反油酸具有一个线性结构，熔点是45 ºC（顺式结构是32 ºC）。