2. Fatty acids are a class of compounds containing a long hydrocarbon chain and a terminal carboxylate group 2. 1 Fatty acids can be saturated or unsaturated. 2.1.1 Saturated fatty acids do not contain carbon-carbon double bonds 2.1. The two most common saturated fatt acids are palmitic and stearic acids (软脂酸和硬 脂酸) containing 16 and 18 carbons respectively (abbreviated as 16: 0 and 18: 0). 2.1.3 Unsaturated fatty acids contain one or more carbon-carbon double bonds, usually of cis configuration in the aliphatic 脂肪族的 chains。2. Fatty acids are a class of compounds containing a long hydrocarbon chain and a terminal carboxylate group 2.1 Fatty acids can be saturated or unsaturated. 2.1.1 Saturated fatty acids do not contain carbon-carbon double bonds. 2.1.2 The two most common saturated fatty acids are palmitic and stearic acids（软脂酸和硬 脂酸）, containing 16 and 18 carbons, respectively (abbreviated as 16:0 and 18:0). 2.1.3 Unsaturated fatty acids contain one or more carbon-carbon double bonds, usually of cis configuration in the aliphatic（脂肪族的） chains