BRAINCAKEPili and Flagella
Many bacteria have thin projections from their surface: pili and flagella. They are made of protein and extend through the cell wall and capsule.
Pili (singular: pilus)
Pili are short, thin, hair-like protein projections, often covering the whole cell surface. Their functions are:
• Attachment: pili let bacteria stick to surfaces, including host cells, for example the cells lining the urinary tract or gut. This helps pathogenic bacteria to colonise the host and not be washed away.
• Conjugation: a longer sex pilus links two bacteria, and a copy of a plasmid can pass from one cell to the other. This allows genes, such as those for antibiotic resistance, to spread between bacteria, even between different species.
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Key terms in this lesson
- plasmid
- A small, circular loop of DNA in the cytoplasm of a bacterium, separate from the main chromosome, that can replicate independently.
More in Prokaryotic Cells
- Bacterial Cell
- Cell Surface Membrane
- Plasmids
- Nucleoid
- 70S Ribosomes
- Gram-Staining
- Antibiotics
- Alternative Classification of Bacteria
All 31 lessons in Prokaryotic Cells · All Edexcel AS-level Biology topics