A striking shape was recently observed for the cellular organelle endoplasmic reticulum (or “ER”), which consists of stacks of flat sheets connected by helical ramps. This shape is interesting both for its biological function (the ER is the site of protein synthesis through a large fraction of the cell’s ribosomes), and its geometric properties that may be insensitive to details of the microscopic interactions. Surprisingly, we find very similar shapes in molecular-dynamics simulations of the nuclear-pasta phases of dense nuclear matter that are expected deep in the crust of neutron stars — this despite the fact that nuclear pasta is 14 orders of magnitude denser than the aqueous environs of the cell nucleus, and that it is governed by strong interactions between protons and neutrons, while cellular-scale biology is dominated by the entropy of water and complex assemblies of biomolecules. Nonetheless the very similar geometry suggests both systems may have similar coarse-grained dynamics and that the shapes are indeed determined by geometrical considerations, independent of microscopic details. These so-called Terasaki ramps may impact the thermal and electrical conductivities, viscosity, shear modulus, and breaking strain of neutron star crust. Even more surprisingly, the interactions we use may provide a simple model of other biologically important cellular shapes.
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