Prokaryotes and eukaryotes: two ways cells are built

In short: All living things are made of one of two basic cell types: prokaryotes have no nucleus, while eukaryotes have a nucleus and many separate cell compartments. Bacteria are prokaryotes, whereas humans, animals, plants and fungi are eukaryotes.

In more detail: Prokaryotic cells are usually much smaller and more simply built. Eukaryotic cells are divided into compartments with their own tasks, much like a house with different rooms.

In detail

• Who belongs where: Prokaryotes include bacteria and archaea; eukaryotes include animals, plants, fungi and many single-celled organisms such as amoebae or paramecia.
• Genetic material: In prokaryotes the DNA lies freely inside the cell, usually as a circular chromosome, often supplemented by small DNA rings called plasmids; in eukaryotes it is packed into several chromosomes in the nucleus.
• Size: Prokaryotes usually measure only a few thousandths of a millimetre, while eukaryotic cells are generally many times larger.
• Organelles: Eukaryotes have membrane-bound organelles such as mitochondria, the Golgi apparatus and the endoplasmic reticulum, and plants also have chloroplasts; prokaryotes have no such organelles.
• Ribosomes: Both cell types have ribosomes for making proteins, but prokaryotic ones are smaller and built differently, which is why some antibiotics can target only them.
• Cell wall: Many bacteria have a cell wall made of murein, plants one of cellulose and fungi one of chitin; animal cells have no cell wall.
• Reproduction: Prokaryotes usually simply split into two halves, which can happen very quickly; eukaryotes, by contrast, distribute their chromosomes in a more elaborate nuclear division.
• Endosymbiotic theory: Mitochondria and chloroplasts very probably descend from bacteria that were once taken up by a larger cell; this is supported by the fact that they have their own DNA, their own ribosomes and a double envelope (zelle-aufbau-und-funktion, bakterien-und-viren-unterschied, mikroskop-und-mikroorganismen).