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Cilia and Flagella

Cilia and flagella are two cell organelles primarily found in protozoa, such as amoeba, paramecium, and euglena. However, they are also found in other microorganisms, such as bacteria, algae, and fungi, and in animals, except for higher plants. 

They are motile cellular appendages made of microtubules and remain covered by the plasma membrane. Both cilia and flagella aid in movement.

Cilia and Flagella

Compare and Contrast Cilia and Flagella

Although cilia and flagella share many characteristics, they are also different in a number of ways.

Difference between Cilia and Flagella

Cilia are short, microscopic, hair-like structures or organelles extending in large numbers from the surface of eukaryotic cells. In contrast, flagella are long, complex filamentous cytoplasmic structures protruding through the cell wall.

1. FoundOnly in eukaryotes such as areas of the respiratory tract and female reproductive trackBoth eukaryotes and prokaryotes
2. Composed OfPolymers of globular proteins called tubulin, the motor protein called dynein, and nexin  Polymers of tubulin and dynein. Bacterial flagella also contain flagellin
3. Structure and Organization  Length: Short, hair-like, (5-10)µ in length   Thickness: Around 0.3 to 0.5 μm in thickness
Organization: Possess a central bundle of microtubules called the axoneme 9 outer doublet microtubules surround a central pair of singlet microtubules When viewed under an electron microscope, the cross-section of the axoneme shows the characteristic 9 + 2 arrangement  
Length: Long, whip-like, or thread-like organelle. 150µ in length
Thickness: Around 0.02 to 0.025 μm in thickness
Organization: Eukaryotic flagella are remarkably similar in their organization to cilia, showing the characteristic 9 + 2 arrangement of microtubules
Prokaryotic flagella are simpler structures made up of flagellin       
4. FunctionsHelps primarily in locomotion. It also helps in feeding circulation, aeration, and respiration Help mainly in locomotion
5. Beating PatternComplicated, can move in a wide range of motionsCircular, wave-like, or propeller-like motion
6. Distribution in CellDistributed throughout the cell surfacePresent at one end or two ends or all over the surface
7. DensityNumerous, approximately hundreds per cellFewer than cilia, less than 10 per cell
8. Energy RequirementUse ‘kinesin,’ having an ATPase activity that produces energy to perform the movementPowered by the proton-motive force generated in the plasma membrane in prokaryotes. It is ATP-driven in eukaryotes
9. Position In CellPresent throughout the surface of the cellEither present at both the ends of the cell or all over the surface  
10. TypesTwo types: motile or non-motileThree types: bacterial, archaeal, and eukaryotic
11. Types of Motiona) Rotational, like a motor b) Very fast-movinga) Wave-like, sinusoidal undulating movement b) Slow moving
12. Beating PatternBeating in a coordinated rhythm either simultaneously (synchronous) or one after the other (metachronous)Beating is independent of each other
13. Cross sectionNexin arm presentNexin arm absent

How are Cilia and Flagella Alike

Although they differ in many aspects, cilia and flagella have similarities. They are

  • Function primarily in locomotion.
  • Arise from the basal body, a centriole-like structure
  • Develop from the cell’s plasma membrane
  • Have an axoneme, a central filament. Axoneme has 11 microtubules, of which 9 are in pairs (doublet), and the remaining 2 are located in the center (singlet)., showing the typical 9+2 arrangement of microtubules


Cilia and flagella are two significant microscopic appendages of cells. Cilia are present in both animals and microorganisms but absent in higher plants. In contrast, flagella are used for mobility in bacteria and gametes (sperm and egg cells) of eukaryotes. Both cilia and flagella serve locomotory functions but in different manners. Both rely on dynein, a motor protein, and microtubules to work.

Article was last reviewed on Wednesday, February 1, 2023

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