A level Biology exam revision resources written by A level Examiners


All bacterial cells are prokaryote, which is why the kingdom of bacteria is called Prokaryotae. It would be a mistake to view this type of cell as inferior to the eukaryote, or less significant numerically. There is a greater variety and biomass of bacteria on the planet than all the other four kingdoms (plants, animals, fungi and protists) put together.

Prokaryotes are generally smaller than eukaryotes and they contain very few membrane bound organelles.

The same as in eukaryotes.

Plasma membrane
The same as in eukaryotes.

The same as in eukaryotes.

Nuclear Zone
The region of the cytoplasm that contains chromosome. The chromosome is a single closed circle of DNA with attached proteins.

A small circlet of DNA which reproduces independently of the main chromosome. Plasmids can pass between cells exchanging genes. This feature is very important in genetic engineering.

These are small (70s) ribosomes. They are free in the cytoplasm.

Cell Wall
Made of a glycoprotein (murein)

Slime Layer
A thick polysaccharide layer outside of the cell wall.

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