question: Free fatty acids are carboxylic acids that contain long chains of what?
distractor3: particles
distractor1: vapors
distractor2: lipds
correct_answer: hydrocarbons
support: In the Figure below , we see the structures of some common classes of lipids. Free fatty acids are carboxylic acids that contain long hydrocarbon chains. Saturated fatty acids are alkanes with a single carboxylic acid, whereas unsaturated fatty acids contain one or more C-C double bonds. Fatty acids often form esters with one of the alcohol functional groups on glycerol , a three carbon chain in which each carbon is bonded to one OH group. Triglycerides are common structures, in which all three of these OH groups are esterified with a fatty acid. The three fatty acids in a triglyceride may be the same or different. Another common structure is a phospholipid, in which two of the alcohols in glycerol form esters with fatty acids, and the third is connected to a very polar phosphorus-containing group.