Membrane Fluidity: Both Fundamental and Functional

Abstract

It has been known for decades that cells actively sense and regulate the fluidity of their membranes. Sinensky coined the phrase “homeoviscous adaptation” to describe the process, after observing that bacteria grown at different temperatures maintain constant membrane fluidity via changes in lipid composition. Homeostatic membrane changes have subsequently been demonstrated across the kingdoms of life and in response to other environmental changes, such as hydrostatic pressure or salinity. However, the viscosity of a lipid membrane is both phenomenologically richer and more challenging to measure than that of a fluid in three dimensions.