Role of Biophysics in Understanding Cellular Membrane Structure and Dynamics

Abstract

Cellular membranes are not passive barriers but highly organised, dynamic assemblies of lipids and proteins whose physical properties regulate signalling, transport, adhesion and cell shape. Biophysics has been central to revealing how these properties arise and how they are controlled. This paper examines the contribution of biophysical approaches to understanding membrane structure and dynamics, drawing on literature published between 2015 and 2025 and on a representative integrated dataset. The approaches considered include X-ray and neutron scattering, environment-sensitive fluorescence spectroscopy, fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS) and super-resolution STED–FCS, single-particle tracking (SPT), atomic force microscopy (AFM), micropipette aspiration of giant vesicles, cryo-electron microscopy and molecular dynamics (MD) simulation. A descriptive and comparative design was adopted in which literature-reported parameters were synthesised and organised into a coherent model dataset covering bilayer structure, lipid packing, lateral diffusion and cholesterol-dependent remodelling. Increasing cholesterol from 0 to 40 mol% reduced the area per lipid by 25.2%, increased bilayer thickness by 5.5 Å and more than doubled bending rigidity. Laurdan generalised polarisation distinguished gel, liquid-ordered and liquid-disordered states and captured the sharp main phase transition of DPPC near 41 °C. Lateral diffusion coefficients spanned almost two orders of magnitude, from 8.2 µm²/s in pure fluid vesicles to 0.11 µm²/s for transmembrane proteins in the plasma membrane, reflecting the combined effects of lipid order, crowding and cytoskeletal compartmentalisation. The analysis demonstrates that integrating structural, spectroscopic, mechanical and computational methods is essential for linking the molecular composition of membranes to their emergent behaviour in living cells.