The double bonds in naturally occurring fatty acids present in our body are in cis configuration while the enzymes for beta oxidation can act on trans double bond. Then what will be the significance of cis double bond in naturally occurring fatty acids? Why the naturally occurring fatty acids don't have double bond in trans configuration?
The diversity of fatty acids produced by an organism is limited by the diversity of enzymes which synthesize them. Unsaturated fatty acids contain carbon-carbon double bonds which do not isomerize. The capacity for humans to produce cis fatty acids is probably selected for because of their lower melting point which prevents arterial clogging. Cold blooded animals utilize cholesterol to increase membrane fluidity when their body temperature is low.