Enhancing Membrane Fluidity with Fatty Acids

In biological membranes, phospholipids play a crucial role in maintaining structural integrity and fluidity. These molecules typically consist of a hydrophilic (water-attracting) 'head' and two hydrophobic (water-repelling) 'tails'. The arrangement of these phospholipids forms a bilayer that serves as a barrier to protect cellular components. Within this hydrophobic environment, certain types of molecules are able to diffuse through the membrane more easily than others.

Consider the differences in membrane permeability among various lipid types and how factors like chain saturation and length affect this property. Specifically, saturated fatty acids, unsaturated fatty acids, and different types of phospholipids contribute uniquely to membrane fluidity and permeability.

Which of the following types of fatty acids or their derivatives would most likely enhance membrane fluidity at physiological temperatures?