# Bacterial Cell Structure

> A bacterium is a prokaryote: it has no membrane-bound nucleus. Its DNA sits in the nucleoid region, and the cell is protected by a wall and often a capsule, with pili and flagella on the outside.

Web page: https://cellnaut.com/topics/bacterial-cell-structure

![Teaching illustration: Bacterial Cell Structure](https://cellnaut.com/texture-references/gpt-image-2-biology-more-teaching-2026-05-31/jpg/bacterial-cell-structure-teaching.jpg)

## Labelled parts

1. **Capsule**: A sticky outer layer that helps resist drying and immune attack.
2. **Cell wall**: A peptidoglycan wall that holds the cell's shape.
3. **Cell membrane**: Controls what enters and leaves; many reactions happen on it in bacteria.
4. **Cytoplasm**: The gel-like fluid where metabolism takes place.
5. **Nucleoid region**: The region where DNA is concentrated, with no membrane around it.
6. **Circular chromosome DNA**: Most bacteria have a single circular chromosome.
7. **Plasmid**: A small extra circle of DNA that often carries useful genes.
8. **Ribosomes**: Smaller than eukaryotic ribosomes; they build proteins.
9. **Pili**: Hair-like projections for attaching to surfaces and exchanging DNA.
10. **Flagellum**: A rotary motor with a long propeller for swimming.

## Key points

- DNA is a single circular chromosome in the nucleoid, with no nuclear envelope.
- Plasmids are small extra circles of DNA that can carry genes such as antibiotic resistance.
- The peptidoglycan cell wall gives shape and is the target of many antibiotics.

## Check yourself

**1. Where is the DNA of a bacterium found?**

- A. In a nucleus
- B. In the nucleoid region
- C. In mitochondria
- D. In the cell wall

**Answer:** B. In the nucleoid region - Bacteria have no nucleus; the DNA sits in the nucleoid.

**2. What do plasmids often carry?**

- A. The whole genome
- B. Extra genes such as antibiotic resistance
- C. Ribosomes
- D. Chloroplasts

**Answer:** B. Extra genes such as antibiotic resistance - They are small extra loops of DNA that can be shared between bacteria.

## Related lessons

- [What Is a Cell?](https://cellnaut.com/learn/what-is-a-cell)
- [The Cytoskeleton and Cell Movement](https://cellnaut.com/learn/cytoskeleton-and-movement)

## See it in 3D

- [Bacteria Cell](https://cellnaut.com/studio/bacteria)
- [Cyanobacterium](https://cellnaut.com/studio/cyanobacteria)