Space-filled representations of eight free fatty acids (FFAs). Saturated FFAs (e.g. lauric and stearic acids) have a simple ‘straight-line’ structure. A cis-double bond causes a kink in the carbon chain (e.g. myristic and oleic acids). Additional cis-double bonds in the carbon chain cause further kinks (e.g. linoleic, γ-linolenic and eicosapentaenoic acids). However, trans-double bonds have little effect on the shape (e.g. elaidic acid), and these FFAs structurally tend to resemble saturated FFAs (e.g. stearic acid)