see the video
M. Rahimi and M. Arroyo, Phys. Rev. E 2012
Organelles and cells are often placed out of equilibrium by localized density disturbances caused by a myriad of physicochemical phenomena. Proteins or polymers inserting into the bilayer, effectively changing the lipid packing, can induce shape changes. Lipid molecules can locally change their shape and size, for instance under localized pH alterations,leading to transient shape changes. Lipid translocation between the monolayers driven by flippases can induce budding. This video illiustrates how the insertion/extraction of a molecule in one monolayer locally increase the lipid density monolayer, by mobilizing interlayer slippage and curvature elasticity.