Flagella- Definition, Structure, Types, Arrangement, Functions, Examples


Flagella are hair-like or whip-like structures that protrude from the cell membrane and are composed of protein. They are used to propel cells through liquid, especially bacteria, archaea, and some eukaryotes like flagellates and sperm . Flagella can vary in number and location on the cell surface . The Latin word flagellum means "whip" to describe its lash-like swimming motion. The flagellum in archaea is called the archaellum to note its difference from the bacterial flagellum .

Flagella are important for various biological functions, such as locomotion, sensing, feeding, and reproduction. They also play a role in the colonization of tissue surfaces and the virulence of some pathogens. Flagella can respond to different stimuli, such as chemical, thermal, or mechanical signals, and change their direction or speed of movement accordingly.

Flagella have different structures, compositions, and mechanisms of propulsion across the three domains of life: Bacteria, Archaea, and Eukaryota. However, they all share the same function of providing motility. The three types of flagella are bacterial, archaeal, and eukaryotic. The flagella in eukaryotes have dynein and microtubules that move with a bending mechanism. Bacteria and archaea do not have dynein or microtubules in their flagella, and they move using a rotary mechanism. Other differences among these three types will be discussed in detail in the following sections.

In this article, we will explore the definition, structure, types, arrangement, functions, and examples of flagella in different organisms. We will also compare and contrast the similarities and differences among the flagella of different domains of life. By the end of this article, you will have a better understanding of the diversity and complexity of these fascinating cellular appendages.