One of the most fundamental functions of the cellular membrane is to enable the cell to maintain the electrochemical gradients essential for life. A large part of the processes and energy expenditure, up to 60% , in a cell are spent on maintaining these transmembrane gradients, which can then be used to drive essential cellular functions. This is only possible due to the particular permeability of the lipid membrane. Only small non-charged molecules, such as water, can to any meaningful degree cross the membrane through passive diffusion. Ions and larger molecules require facilitated diffusion or active transport, which is carefully regulated by various protein channels and transporters. There is also evidence that prokaryotic cells, like bacteria, dedicate a larger proportion of their energy production to transmembrane transport, compared to eukaryotic cells .