BioMasterCilia, flagella and the structures of the cell surface
A classic General Biology question: when you see multiple structures around a cell, are they cilia or flagella? Settle it in 2 minutes, with a comparison table and exam traps.
Direct answer: The multiple, short structures surrounding the cell are cilia. Flagella are long and few (one or a few per cell). Both share the same internal microtubule structure (the 9+2 axoneme), but they differ in length, number and type of movement.
What projects from the cell surface?
- Cilia — motile projections that are short and numerous.
- Flagella — motile projections that are long and few (typically 1).
- Microvilli — non-motile projections that increase the absorptive surface.
- Glycocalyx — outer carbohydrate coat for cell recognition and protection.
- Cell wall — rigid supporting cover in plants, fungi and bacteria.
Cilia vs. flagella: comparison table
| Feature | Cilia | Flagella |
|---|---|---|
| Length | Short (2–10 µm) | Long (up to 200 µm) |
| Number per cell | Many (hundreds) | One or a few |
| Movement | Rowing stroke, coordinated | Whip-like, undulating |
| Internal structure | 9+2 axoneme | 9+2 axoneme |
| Example | Respiratory epithelium | Sperm tail |
Internal structure: the 9+2 axoneme
- 9 outer doublets of microtubules + 2 central → the 9+2 pattern.
- Anchored in the basal body (9+0 structure, like a centriole).
- Movement is generated by the motor protein dynein, using ATP.
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Study Biology free on BioMasterFrequently asked questions
Which multiple structures surround the cell?
The multiple, short surface structures are cilia. If they are long and few, they are flagella.
What is the difference between cilia and flagella?
Cilia are short and numerous and beat like oars; flagella are long and few and move by undulating. Both have a 9+2 axoneme.
Are cilia and microvilli the same thing?
No. Cilia move (microtubules, 9+2); microvilli do not move (actin) and are used for absorption.