Prokaryotic Cell Structure (Bacterium)

 

The most fundamental divide in living organisms is the division into prokaryotes and eukaryotes.

Eukaryotes have the formed cell nucleus, which lack the prokaryotes.

Here we see a bacterium cell structure (bacteria are prokaryotes) with DNA in its center, but not forming a nucleus.

The point is not just to have or not to have the nucleus, but in prokaryotes most of the cellular processes work in fundamentally different way than in eukaryotes.