All life on earth is divided into three domains - bacteria, archaea, and eukarya. The domains archaea and bacteria make up the prokaryotes, single-celled organisms that lack a nucleus. In contrast, the eukaryotes (eukarya) are single or multi-celled organisms, the cells of which contain a nucleus and membrane-bound organelles. Eukaryotes include everything from the unicellular algae and yeasts to the multicellular plants and animals. We’ll discuss more of the defining features of prokaryotes and eukaryotes below.
Prokaryotic cells are typically smaller than eukaryotic cells, with a diameter generally between one to 10 micrometers (though there are some exceptions!). These cells have a relatively simple structure, consisting of a membrane around the cytoplasm, ribosomes (molecules that help make proteins) freely floating in the cytoplasm, and a nucleoid, an area within the cytoplasm that contains the cell’s DNA. This DNA is typically arranged as a single, circular chromosome. Most bacteria also have a cell wall made out of peptidoglycan (a protein/carbohydrate polymer), which maintains the cell’s shapes and protects it from dehydration. Some prokaryotic cells also have a flagellum (a whip-like extension used for movement); if present, the flagellum is made of the protein flagellin. The surface of prokaryotic cells can also contain a hair-like extension called a pilus, which allows cells to transfer DNA directly with one another.
In contrast, eukaryotic cells are larger (generally, between 10 and 100 micrometers) and more complex than prokaryotic cells. One defining feature of eukaryotic cells is the presence of a membrane-bound nucleus which houses the cell’s genetic material. Within the nucleus, the DNA of eukaryotes is typically arranged in many linear chromosomes (in contrast to the single circular chromosome of prokaryotes) - a eukaryotic cell can have up to 1260 chromosomes, though this number varies widely among species. Unlike prokaryotic cells, eukaryotic cells have membrane-bound organelles, which are specialized compartments within the cytoplasm that perform specific functions (for example, the mitochondria of eukaryotic cells are involved in energy production). Like prokaryotes, eukaryotes cells also have ribosomes for protein production, but, in addition to being freely floating in the cytoplasm, the ribosomes are also found attached to the endoplasmic reticulum, an organelle involved in protein and lipid modification and transport. Some eukaryotic cells also have flagella for movement, but these flagella are made out of microtubules, not flagellin. If a cell wall is present (for example, as it is in fungi and plant cells), it’s made out of chitin (a type of polysaccharide found in fungi) or cellulose (in plants). Eukaryotic cells do not have pili, and cannot directly exchange DNA the same way prokaryotes can.
While the the presence of membrane-bound organelles, organization of the genetic material, and presence of a membrane-bound nucleus are the major features distinguishing prokaryotes and eukaryotes, these groups also differ in the size of their ribosomes (70S in prokaryotes and 80S in eukaryotes), how they reproduce (by binary fission in prokaryotes, and by mitosis and meiosis/sexual reproduction in eukaryotes), and some aspects of how their DNA is translated into proteins. Comparing features like these between prokaryotes and eukaryotes is one way scientists try to understand evolution of life on earth: the general view (called the endosymbiotic theory) is that eukaryotes were created when one prokaryote engulfed another (in fact, the mitochondria of eukaryotic cells is thought to have descended from the “eaten” prokaryote), but it’s important to note that the exact relationship between the two is an area of ongoing research.
https://evolution.berkeley.edu/evolibrary/article/_0/endosymbiosis_03
https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookmito.html
Prokaryotic cells do not have a nucleus. They do have genetic material, but it is not as organized. In the theory of evolution, prokaryotic cells are considered the beginning of life. Prokaryotic cells have their genetic material inside of a nucleoid. Bacteria are examples of prokaryotic cells. Transcription, the process by which new DNA is formed, takes place inside the cytoplasm. This DNA is circular. Prokaryotic cell walls, if applicable, contain peptidoglycan.
Eukaryotic cells have a nucleus which contains their genetic material. This allows for greater complexity, as these cells also have different organelles within them, such as mitochondria and ribosomes. Transcription in eukaryotic cells takes place inside of the nucleus. DNA in eukaryotic cells is linear. Eukaryotic cell walls are composed of cellulose. This is applicable for plant cells only.
https://www.majordifferences.com/2013/08/difference-between-prokaryotic-cell-and_27.html
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