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The Prokaryotic Cell Single cell organisms that lack a nuclear membrane Small in size 1-10 micrometres The Prokaryotic Cell Prokaryotic cells divide by binary fission. This is an asexual method of reproduction in which a 'parental' cell divides into two smaller but equally sized cells. The cells are genetically identical and form the basis of a reproductive clone. Binary Fission (a). Reproduction signal:. E.coli replicates about once every 40 minutes when incubated at 37o C. (b). Replication of DNA: bacterial cells have a single condensed loop of DNA. This is copied by a process known as semi-conservative replication to produce two copies of the DNA molecule one for each of the daughter cells (c). Segregation of DNA: One DNA loop will be provided for each of the daughter cells. (d). Cytokinesis: Cell separation Prokaryotic Cell Population growth by binary fission will be exponential: as time increases, the rate of growth of population increases (until there are not more resources for extra growth) 70s versus 80s in the Eukaryotic Cell E. Coli EM Note the double membrane of this E. coli . This feature means that the cells do not retain the dark blue stain used in microscopy. They are therefore known as Gram-negative this contrast with Grampositive single membrane bacteria. 2. There is some evidence in the image of pilli which are the surrounding light grey masses. 3. In the cytoplasm of the bacterium there are no visible organelles which is consistent with how we expect a prokaryote cell to appear. 4. The nucleoid region is not seen well in this particular image but is clearer in the next image. The Prokaryotic Cell Characteristics include: No true distinct nucleus No complex, membranous organelles (Ribosomes only) Most have cell walls Flagella (rotary type structure & not composed w/microtubules) Pili used to transfer DNA from one cell to another (sexual reproduction) The Prokaryotic Cell Characteristics include: Nucleoid (region containing free DNA) Classified according to their metabolic needs Divide by binary fission No mitochondria Exercises What is a disadvantage of the prokaryotic cells having their DNA free in the cytoplasm without a nuclear membrane What structures are involved in sexual reproduction in prokaryotic cells A bacterium walked into a restaurant. “I’d like a pizza please” he said “I’m sorry, we’re not doing food today,” the waiter replied WHY NOT?? “We don’t have the staph” Read and outline prokaryotic cells from your text Stem Cells Review Prokaryotic Assessment Statement