# Prokaryotic cell

A small, simple cell with no nucleus. Its DNA floats in a region called the nucleoid. Bacteria and archaea are prokaryotes.

Biology (university) · Part 01: Cell structure and membranes · Card 1 of 9 · Last updated 2026-10-19

## Analogy

A studio flat: one open room where everything happens.

## Example

**Size check**

Typical bacterium: 1 to 5 micrometres.
Typical animal cell: 10 to 30 micrometres.
So a human cell is roughly 10 times wider.

## In practice

Antibiotics such as penicillin target bacterial cell walls, which human cells do not have.

## Practice

### Flashcards

- **Which two features separate prokaryotic from eukaryotic cells?** Eukaryotes have a nucleus and membrane-bound organelles. Prokaryotes have neither.
- **What is the nucleoid?** The region of a prokaryotic cell where its DNA sits. It is not enclosed by a membrane.

### Interview questions

**Compare the structure of prokaryotic and eukaryotic cells and explain why compartments help eukaryotes.**

- Prokaryotes lack a nucleus and membrane-bound organelles
- Eukaryotes keep DNA in a nucleus and have organelles
- Compartments keep incompatible reactions apart
- Compartments raise efficiency by concentrating enzymes

## Questions people ask

### Do prokaryotes have any organelles at all?

Prokaryotes have no membrane-bound organelles, but they are not empty. They have ribosomes that build proteins, a nucleoid holding DNA, and often a cell wall and a tail called a flagellum. Some bacteria even have simple protein-walled compartments for specific jobs.

### Are bacteria and archaea the same thing?

No. Both are prokaryotes, but they are separate domains of life with different chemistry. Archaea have different membrane lipids and cell walls, and their gene machinery is closer to that of eukaryotes. Many archaea live in extreme places such as hot springs, though many live in ordinary soil and oceans too.

## Related concepts

- [Eukaryotic cell](https://studyvisually.com/learn/science/biology-university/biology-university-part-1/biology-university-part-1-concept-2)
- [Nucleus](https://studyvisually.com/learn/science/biology-university/biology-university-part-1/biology-university-part-1-concept-3)

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