Category talk:Eukaryotes

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Prokaryotes are organisms without a cell nucleus. Eukaryotic Organisms have a nucleus. The cell structure of prokaryotes differs greatly from eukaryotes in many ways. The defining characteristic is, of course, the absence of a nucleus. Prokaryotes also lack cytoskeletons and do lack membrane-bound cell compartments such as vacuoles, endoplasmic reticulum, mitochondria and chloroplasts. In eukaryotes, the latter two perform various metabolic processes and are believed to have been derived from endosymbiotic bacteria. In prokaryotes similar processes occur across the cell membrane. Prokaryotes have a single circular chromosome, contained within a region called nucleoid, rather than in a membrane-bound nucleus, but may also have various small circular pieces of DNA called plasmids spread throughout the cell. While prokaryotes are nearly always unicellular, some are capable of forming groups of cells called colonies. Unlike many eukaryotic multicellular organisms, each member of the colony is undifferentiated and capable of free-living. Colonies are formed by organisms that remain attached following cell division, sometimes through the help of a secreted slime layer. The prokaryotes is different to the eukaryote other than in the membrane bound organelles in that the DNA in the eukaryote is found in the nucleus while in the prokaryote there is only a single loop of DNA. Eukaryotic cells are generally much larger than prokaryotes, typically a thousand times by volume. They have a variety of internal membranes and structures, called organelles, and a cytoskeleton composed of microtubules and microfilaments, which play an important role in defining the cell's organization. Eukaryotic DNA is divided into several bundles called chromosomes, which are separated by a microtubular spindle during nuclear division. In addition to asexual cell division, most eukaryotes have some process of sexual reproduction via cell fusion, which is not found among prokaryotes.