Teaching Biophysics II. Biophysical approach of transport through cellular membranes

Abstract

Cellular metabolism implies a permanent transport through membranes of a great diversity of particles (e.g., ions, molecules, macromolecules, protein vesicles, etc.) in and out of the cells. The transport phenomena can be classified as passive (down the concentration gradients, driven solely by thermal agitation) or active (against the concentration gradients, driven by an energy supply) and selective (i.e., through specific pathways) or nonselective through membrane lipid bilayers. This paper will describe in an accessible manner all the types of membrane transport from a biophysical point of view along with their crucial roles in normal cellular functioning. This paper is the successor of a previous work (A. I. Popescu, C. G. Chilom, Rom. Rep. Phys. 75, 605 (2023), Ref. [1]) in a series aiming to disseminate Biophysics in an accessible manner.