A flagellum (plural: flagella)'s a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and functions in locomotion. There're some notable differences between prokaryotic and eukaryotic flagella, such as protein composition, structure, and mechanism of propulsion. An example of a flagellated bacterium's the ulcer-causing Helicobacter pylori, which uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium. An exa… (More on Flagellum)