What happens to membrane fluidity when the fatty acid chains are shortened?
Fluidity of biomembranes reflects balance between van der Waals cohesion and steric freedom of acyl chains introduced by kinks. Shortening fatty acid chains from eighteen to fourteen carbons reduces surface area for London dispersion forces, weakening chain chain attraction and lowering cooperative melting enthalpy and phase transition temperature. The transition temperature Tm drops sharply, so at physiological thirty seven degrees a larger fraction exists in liquid crystalline disordered state characterized by frequent trans gauche isomerizations and rapid lateral diffusion near ten to minus
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 10: Fatty acid chain length and membrane fluidity.
