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Abstract

All biological cells are enclosed by a fluid membrane and have to continuously transport information and material across this interface. Cells have developed multiple strategies by which they take up small particles. In this thesis, I use theoretical models from statistical physics and computer simulations to investigate two of these strategies, namely receptor-mediated endocytosis driven by adhesion energy and clathrin-mediated endocytosis driven by the polymerisation energy of supramolecular assembly. For receptor-mediated uptake, I focus on systems with sizes in the order of 10 − 300 nm, few tens of cell surface receptors and address stochastic effects. We show how the stochastic dynamics of uptake is influenced by particle geometry and compare theoretically predicted adhesion energies to experimental data. For clathrin-mediated endocytosis we demonstrate by combining different experimental data sets with physical models how clathrin triskelia assemble and rearrange during endocytosis. Using computer simulations we show that flat clathrin lattices grow sparsely and that an increasing clathrin density could drive a flat-to-curved transition of clathrin lattices. Together, these results demonstrate how physical models can help to understand the complex biological process of cellular uptake.