2.1.4 Positions of double bonds are specified by superscript numbers following a 4 symbol,eg, linoleic acid(亚油酸)is abbreviated as 18: 2(49 12). 2. 1. 5 The number of carbons in a fatty acid is commonly even and the positions of carbon- carbon double bonds are regular (usually at positions 9, 12, 15(+3), separated by a methylene roup and never conjugate, that is, alternating gI single and double bonds).(cis)
2.1.4 Positions of double bonds are specified by superscript numbers following a symbol, e.g., linoleic acid（亚油酸）is abbreviated as 18:2(9,12). 2.1.5 The number of carbons in a fatty acid is commonly even and the positions of carboncarbon double bonds are regular (usually at positions 9, 12, 15 (+3), separated by a methylene group and never conjugate, that is, alternating single and double bonds). (cis)
216 Oleic acid(油酸),18:1(Δ”),is the most common monounsaturated fatty acid in mammals 2.1.7 Linoleic acid, 18: 2(4, 12), and linolenic acid (亚麻酸),18:3(△9121),can not be synthesized by mammals and are called essential fatty acids(like vitamins, they have to be taken from food)
2.1.6 Oleic acid（油酸）, 18:1(9 ), is the most common monounsaturated fatty acid in mammals. 2.1.7 Linoleic acid, 18:2(9,12), and linolenic acid（亚麻酸）, 18:3(9,12,15), can not be synthesized by mammals and are called essential fatty acids (like vitamins, they have to be taken from food)
2.2 The physical properties of fatty acids are mainly determined by the length and degree of unsaturation on the hydrocarbon chain 2.2. I The shorter the hydrocarbon chain. the lower its melting point(saturated fatty acids of 10 or less carbon atoms are liquid, of 12 or more carbons are waxy or solid at room temperature). 2. 2. 2 Existence of carbon-carbon double bonds lowers the melting point of fatty acids due to the kink introduced by double bonds (therefore preventing the tight packing)
2.2 The physical properties of fatty acids are mainly determined by the length and degree of unsaturation on the hydrocarbon chain. 2.2.1 The shorter the hydrocarbon chain, the lower its melting point (saturated fatty acids of 10 or less carbon atoms are liquid, of 12 or more carbons are waxy or solid at room temperature). 2.2.2 Existence of carbon-carbon double bonds lowers the melting point of fatty acids due to the kink introduced by double bonds (therefore preventing the tight packing)
2.3 Fatty acids are usually four components of complex ipide d as 2.3.1 Fatty acids are major oIs components of the triacylglycerols, th common storage lipids. 2.3.2 Fatty acids are also components of the membrane phospolipids and glycolipids. 2.3.3a small amount of free fatty acids are carried by serum albumin(血清台蛋白) in the blood of vertebrate animals
2.3 Fatty acids are usually found as components of complex lipids. 2.3.1 Fatty acids are major components of the triacylglycerols, the common storage lipids. 2.3.2 Fatty acids are also components of the membrane phospolipids and glycolipids. 2.3.3 A small amount of free fatty acids are carried by serum albumin（血清白蛋白） in the blood of vertebrate animals
2.4 Triacylglycerols are fatty acid esters of lucero l甘油) and provide stored energy and insulation 2.4.1 Triacylglycerols are nonpolar hydrophobic, and essentially insoluble in water 2.4.2 Triacylglycerols serve as stored energy in animal adipocytes (fat cells)and plant seeds. 2.4.3 Oxidation of triacylglycerols yields more than twice the amount of energy than carbonhydrates or proteins, gram for gram(due to the higher level of reduction of he acyl(酰基)gi s). roups
2.4 Triacylglycerols are fatty acid esters of glycerol（甘油） and provide stored energy and insulation. 2.4.1 Triacylglycerols are nonpolar, hydrophobic, and essentially insoluble in water. 2.4.2 Triacylglycerols serve as stored energy in animal adipocytes (fat cells) and plant seeds. 2.4.3 Oxidation of triacylglycerols yields more than twice the amount of energy than carbonhydrates or proteins, gram for gram (due to the higher level of reduction of the acyl（酰基） groups)