Two kinds of cell
Show on a big screenA bacterium and a mango tree are both alive. Where does each keep its DNA?
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The rule
A mango cell keeps its DNA in a nucleus. A bacterium's DNA lies loose in the cytoplasm.
A cell with its DNA in a nucleus is eukaryotic. A cell with its DNA loose in the cytoplasm is prokaryotic. A prokaryotic cell has no membrane-bound organelles.
A eukaryotic cell has a true nucleus, with a membrane round it. A prokaryotic cell has no such nucleus. Its DNA lies in a region called the nucleoid. Membrane-bound means enclosed by its own membrane.
- Some cells keep DNA in a compartment. Some do not.
- A eukaryotic cell has a nucleus, with its own edge.
- A prokaryotic cell keeps DNA loose, with no compartment.
- Neither one is a lesser cell.
Side by side
| Prokaryotic | Eukaryotic | |
|---|---|---|
| Cells in one organism | Usually one | One or many |
| Where the DNA lies | Loose, in the nucleoid | Inside a nucleus |
| Size | Usually smaller | Usually larger |
| Membrane-bound organelles | No | Yes |
Bacteria are prokaryotic. Yeast, amoeba, plants and animals are eukaryotic. Bacteria have a cell wall. So do plant cells. A wall does not tell you the kind.
Watch out!
A small cell can still have a nucleus. A yeast cell is tiny, and it has one.
Try the lab to finish this lesson.