Structure and Function: Flagella are tiny waving filaments with important functions in humans, such as clearing our airway. Bacterial flagella are powered by proton motive force. Flagella also move liquid over the cell surfaces and are used in movement. The core structure of flagella consists of a central microtubule pair and nine surrounding microtubule doublets that are connected by nexin links. Flagella are filamentous protein structures attached to the cell surface that provide the swimming movement for most procaryotes. Procaryotic flagella are much thinner than eucaryotic flagella.