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Structures of Prokaryotic Cells

Prokaryotic cells are much smaller than eukaryotic cells.

All prokaryotic cells have a cell membrane, cytoplasm, ribosomes and a cell wall.

The cell walls of prokaryotic cells are made out of a different substance to plant and algal cell walls.

Prokaryotic cells do not have a nucleus and they also lack many of the other sub-cellular structures found in eukaryotic cells (such as mitochondria, chloroplasts and vacuoles).

Labelled diagram of a prokaryotic cell. It is a rounded rod shape with a thick cell wall around it. On the inside of the cell wall is the cell membrane. Inside that is the cytoplasm. Within the cytoplasm there are ribosomes, one circular chromosome and a few circular plasmids.

Diagram of a prokaryotic cell, with its sub-cellular structures labelled.

Image of bacterial cells taken through an electron microscope. The image is black and white. One bacterial cell occupies most of the image. Parts of other cells are visible around the edges. Each cell is roughly rod shaped with rounded edges.

Electron microscope image of bacterial cells (which are prokaryotic cells). Applications of Microscopy in Bacteriology - Scientific Figure on ResearchGate. Available from: [accessed 16 Aug, 2021] (CC BY 4.0)

Prokaryotic DNA

The DNA in a prokaryotic cell is loose in the cytoplasm (unlike in eukaryotic cells, where the DNA is enclosed in a nucleus).

Most prokaryotic cells have one large DNA molecule called a chromosome. Unlike the chromosomes found in eukaryotic cells, the chromosome in a prokaryotic cell usually forms a loop.

In addition to the chromosome, many prokaryotic cells also contain small loops of DNA called plasmids.


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What features do all prokaryotic cells share?


What is the DNA like in a prokaryotic cell?


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