# Prokaryote --- **Prokaryotes** are organisms that are classified in the [[domains of life|domains]] [[bacteria]] and [[archaea]]. These organisms are pretty small—for example, a bacteria is about the size of a eukaryote's mitochondria. Not to be confused with [[microbe|microbes]], as there are microbes that are actually eurkaryotes, and viruses also can count as a microbe, even though they aren't prokaryotes or eukaryotes. ## Features of All Prokaryotes The features of prokaryotes that are common across the two domains are these: - lack a discrete, membrane-bound [[nucleus|nucleus]], instead they have their chromosomal DNA "nucleoid" region. - have [[prokaryotic DNA|DNA]] - have [[cytoplasm]] - have [[ribosome|ribosomes]] - have a [[cytoskeleton]] - have a [[plasma membrane|cytoplasmic membrane]] - have a [[cell wall]] ## Features of Only Some Prokaryotes Some features are found in some but not all prokaryotes. - [[plasmid]] DNA - [[flagella]] - [[pili]] - [[capsule]] - [[endospore|endospores]] ## Differences Between Bacteria and Archaea Despite looking very similar to each other from a certain perspective, there are actually many important **disctinctions** between archaea and bacteria. - Bacteria and archaea have very different **[[tRNA]] sequences**. - Bacteria and archaea have very different **[[DNA]] sequences**. - There are clear differences in the **[[cell wall]]** and **[[plasma membrane|cell membrane]]** make up between bacteria and archaea. Additionally, archaea tend to live in extreme environments. ## History Most of life's history is prokayrotic, from 3.6 billion years ago to 1.8 billion years ago, it was all prokaryotes. "Cyanobacteria" started making a lot of oxygen, which is *essential* for the devolopment of eukaryotes. ___