123 School Work

Bacterium and Viruses

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  Structure of a Bacterium and a Virus:
  
  Nucleoid = region of cytoplasm where the chromosomal DNA is located.
  Cytoplasm = area where the functions for cell growth, metabolism, and replication are carried out. It is a gel-like matrix composed of water, enzymes, nutrients, wastes, and gases and contains cell structures such as ribosomes, a chromosome, and plasmids.
  Ribosomes = give the cytoplasm of bacteria a granular appearance. They translate the genetic message in messenger RNA into the production of peptide sequences (proteins).
  Cell Wall = maintains the shape of a bacterial cell.
  Cytoplasmic Membrane = There are numerous proteins moving within or upon this layer that are primarily responsible for transport of ions, nutrients and waste across the membrane
  Capsule = layer of polysaccharide (sometimes proteins) protects the bacterial cell and serves as a barrier against phagocytosis by white blood cells
  Flagella (singular is flagellum) = Flagella are long appendages which rotate in a propeller like motion by means of a "motor" located just under the cytoplasmic membrane which help the bacteria to move
  Pili (singular is pilus) = hollow, hairlike structures made of protein allow bacteria to attach to other cells. A specialized pilus, the sex pilus, allows the transfer from one bacterial cell to another
  
  Nucleic acid (either DNA or RNA, but never both) = RNA and DNA directs two processes: protein synthesis (production of the virus's protein coat) and replication (the process by which RNA copies itself)
  Capsid = a protein shell that encloses the nucleic acid and has three functions: 1) it protects the nucleic acid from digestion by enzymes, 2) contains special sites on its surface that allow the virion to attach to a host cell, and 3) provides proteins that enable the virion to penetrate the host cell membrane and, in some cases, to inject the infectious nucleic acid into the cell's cytoplasm.
  3)      Bacteria, although cells themselves, are different from plant and animals cells in the fact that they do not have a nucleus (with exception to a red blood cell). Also, bacteria are very small in comparison to normal cells (only 1/100th the size)
  Viruses are different from plant and animal cells in the fact that are not actually cells at all...