A characteristic feature of eukaryotic cells is the variety of membrane bound organelles, distinguished by their unique morphology and chemical composition. Despite the differences in membrane composition across organelles, ramified, tubular or sheet-like shapes are generic large scale morphologies observed in internal membranes, which suggest involvement of common underlying principles. While there is detailed knowledge of the molecular processes involved in membrane remodelling at short scales, our understanding of the underlying physical principles governing large scale morphogenesis is still rudimentary.
One important feature of organelles, especially those in the trafficking pathways, is that they are subject to and driven by a continuous flux of membrane bound materials, on time scales comparable to membrane relaxation times. The large scale morphology of the membrane bound compartments could be influenced by these active out-of-equilibrium processes of fission and fusion of material. The other common aspect is that organelles are subject to the action of curvature sensing and curvature generating proteins which modulate local membrane shape. Such proteins now include a variety of bar-domain proteins, coat-proteins and GTPases and are found on most membrane bound organelles and the plasma membrane. In this talk, we will discuss the physical changes that the above two processes induce on the membrane.