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How do cilia and flagella help cells move?
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Biology
A researcher using a microscope to examine a specimen in the laboratory.
Cilia and flagella are specialized organelles that facilitate movement in many living organisms. While they share a similar internal structure—typically consisting of a "nine-plus-two" arrangement of microtubules—they differ in length and distribution.123
Mechanisms of Movement
- Eukaryotic Flagella: These organelles move in a characteristic whiplike, undulatory motion. Waves of movement are generated at the base of the flagellum, allowing organisms to swim through aqueous environments. This process requires energy derived from the breakdown of adenosine triphosphate (ATP), which powers the sliding of microtubules.132
- Cilia: Cilia are generally shorter and occur in large numbers. They move in a coordinated, rhythmic fashion. In many ciliated organisms, the synchronized beating of these organelles along the cell surface creates a metachronal wave, which allows for rapid locomotion.21
- Prokaryotic Flagella: It is important to note that bacterial flagella are distinct from eukaryotic ones; they are composed of the protein flagellin and rotate like a propeller, powered by an ion gradient rather than ATP.123
Beyond individual locomotion, these organelles can move fluid and mucus across cell surfaces, such as within the respiratory tract of vertebrates.2