Prokaryotes
Prokaryotes
Prokaryotes (/proʊˈkæri.oʊts/, from the Greek pro- meaning "before" and karyon meaning "nut" or "kernel") are a group of organisms that lack a cell nucleus (karyon), or any other membrane-bound organelles. They are one of the two primary divisions of life, the other being the eukaryotes, which have a nucleus and membrane-bound organelles.
Etymology
The term "prokaryote" is derived from the Greek words "pro" meaning "before" and "karyon" meaning "nut" or "kernel". This is in reference to these organisms having cells that lack a true nucleus, which is a characteristic feature of eukaryotic cells.
Characteristics
Prokaryotes are typically unicellular, though they can form colonies. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus. However, they do have some non-membrane bound organelles, such as ribosomes. Prokaryotes also have a cell wall that protects them and gives them shape.
Classification
Prokaryotes are divided into two domains: Bacteria and Archaea. Bacteria are the more common type of prokaryote and are found in virtually all environments on Earth. Archaea were originally classified as bacteria, but this was changed when it was discovered that they have a unique set of biochemical and genetic properties.
Reproduction
Prokaryotes reproduce asexually, primarily through a process called binary fission. This process involves the replication of the prokaryote's single DNA molecule, which then attaches to the cell membrane. The cell then grows in size, eventually splitting into two daughter cells.
Role in the Environment
Prokaryotes play a vital role in the biosphere. They are involved in the cycling of nutrients such as carbon, nitrogen, and sulfur. Some prokaryotes, known as extremophiles, are able to live in extreme environments that are inhospitable to most other forms of life.
See Also
External links
- Medical encyclopedia article on Prokaryotes
- Wikipedia's article - Prokaryotes
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