Prokaryotic cells and viruses

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  • Prokaryotic Cells/ Viruses
    • Structure
      • Cytoplasm has no membrane bound organelles. Smaller ribosomes than eukaryotic cell
      • Plasma membrane made of lipids/proteins. Controls movement of substances in/out of cell
      • Cell wall supports/prevents cell from changing shape. Made of murein, a glycoprotein
      • Some have capsule made of slime, helps protect bacteria from attack
      • Plasmids, small loops of DNA. Contain genes for antibiotic resistance
      • No nucleus, instead circular DNA that floats free in cytoplasm
      • Flagellum helps cell move
    • Viruses
      • Nucleic acids surrounded by a protein
      • No plasma membrane, no cytoplasm, no ribosomes
      • Invade/reproduce inside cells of hosts
    • Replication of prokaryotes
      • Binary fission
      • 1: Circular DNA/plasmids replicate. DNA loop replicated once, plasmids more than once
      • 2: Cell gets bigger, DNA loops move to opposite poles of cell
      • 3: Cytoplasm begins to divide, new cell walls begin to form
      • 4: Cytoplasm divides, two daughter cells produced. Each has one copy of circular DNA and variable number of plasmid copies
    • Replication of viruses
      • 1: Use attachment proteins to bind to complementary receptor proteins on surface of host cells
      • 2: Require different receptor proteins on host. Some viruses only infect one type of cell
      • 3: Inject their DNA/RNA into host cell. Causes ribosomes/enzymes to replicate viral particles


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