Answer
The oxygen atom in fatty acid dehydration synthesis comes from a fatty acid and not from glycerol
Work Step by Step
In fatty acid dehydration synthesis, one hydrogen (H+) is removed from glycerol and a hydroxyl (OH-) ion is removed from a fatty acid. These two are joined to form water (H plus OH), H2O, which is eliminated from the new compound molecules.. So the oxygen is derived from a fatty acid molecule.