Question

Which of the following might be a feature(s) of a lipid that has been converted from a fully saturated fatty acid to a fatty acid containing several trans double bonds? Select all that apply.

O The trans fatty acid will be able to pack most closely with unsaturated fatty acids containing cis double bonds, than with saturated fatty acids
O The trans fatty acid will be able to pack more closely with saturated fatty acids, than with unsaturated fatty acids containing cis double bonds
O The trans fatty acid will now have a higher melting temperature compared to the fully saturated precursor
O The trans fatty acid will now have a lower melting temperature compared to the fully saturated precursor

Answer 1

The correct answer is option 2. Trans fatty acids can pack more closely with saturated fatty acids than with unsaturated fatty acids containing cis double bonds, resulting in a higher melting temperature for the trans fatty acid as opposed to its fully saturated precursor.

Step-by-step explanation:

When a fully saturated fatty acid is converted to a fatty acid containing several trans double bonds, certain characteristics change due to the configuration of the hydrogens around the double bonds. Unlike cis fatty acids, trans fatty acids allow the chains to be more linear and pack more closely to one another.

Consequently, the trans fatty acid will be able to pack more closely with saturated fatty acids than with unsaturated fatty acids containing cis double bonds, due to their similar straighter shapes. This closer packing among the saturated and trans unsaturated fatty acids also affects their physical properties, such as melting points. Thus, the trans fatty acid will now generally have a higher melting temperature compared to the fully saturated precursor because the tighter packing increases the strength of the intermolecular forces, requiring more heat energy to melt the substance.