Every cell is surrounded by a membrane, which ensures the internal biochemical milieu and regulates the exchange of substances with its surroundings. In every cell membrane, there are a large number of transporters that allow only one sort of molecule to pass through. In the case of very small molecules, such as water, the responsible transporters form tiny pores in the membrane, which disappear immediately after the process. But how are proteins that are thousands of times larger transported through membranes without creating a large leak?