MICROPARA - Prokaryotic and Eukaryotic Cells

• Prokaryotes - Bacteria, cyanobacteria, archaea
• Prokaryotes - Generally 1-10μm in linear dimension
• Prokaryotes - Anaerobic or aerobic
• Prokaryotes - Few or none; no nucleus
• Prokaryotes - Circular DNA in cytoplasm
• Prokaryotes - RNA and protein synthesized in the same compartment
• Prokaryotes - No cytoskeleton
• Prokaryotes - Chromosomes pulled apart by membrane attachments
• Prokaryotes - Mainly unicellular
• Eukaryotes - Protozoans, Algae, Fungi, Plants, Animals
• Eukaryotes - Generally 5-100μm in linear dimension
• Eukaryotes - Aerobic
• Eukaryotes - Nucleus, Mitochondrion, Chloroplast, ER, Golgi complex, etc.
• Eukaryotes - Linear DNA with noncoding regions in nucleus
• Eukaryotes - RNA in nucleus; protein in cytoplasm
• Eukaryotes - With cytoskeleton
• Eukaryotes - Uses cytoskeletal spindle apparatus
• Eukaryotes - Mainly multicellular, with differentiation in cell types
• Flagellum

  • made up of the protein flagellin.
  • Its shape is a 20 nanometer-thick hollow tube.
  • It is helical and has a sharp bend just outside the outer membrane; this "hook" allows the helix to point directly away from the cell.
• Classification of bacterium according to the number of flagella:

  1. monotrichous bacterium - 1
  2. lophotrichous bacterium - many at one side
  3. amphitrichous bacterium - 1 at both side
  4. peritrichous bacterium - everywhere
• Fimbriae

  can occur at the poles of bacterial cells and they can be evenly distributed over the entire surface of the cell
• Fimbriae

  enables the cells to adhere to surfaces, including those of the other cells; helps the cell to colonize mucus membranes
• Pili

  are used for attachments to surfaces such as tissues

  many pathogens possess pili, which are composed of the protein pilin
• The glycocalyx - composed of a thick, gummy material, serves as a reservoir for nutrients and protects the organism from changes in the environment
• The cell wall - With the exception of mycoplasmas, all bacteria have a semirigid cell wall
• Alcohol dehydrates the peptidoglycan of Gram-positive bacteria, but dissolves the outer membrane of the Gram-negative so they become colorless
• Safranin colors the Gram-negative cells red or pink
• Atypical Cell Walls

  They pass through most bacterial filters

  Their plasma membranes are unique among bacteria in having lipids called sterols, which are thought to help protect them from lysis (rupture).
• Cytoplasm

  About 80% water proteins (enzymes), carbohydrates, lipids, inorganic ions
• Nucleoid - contains a single long, continuous, and frequently circularly arranged thread of double-stranded DNA called the bacterial chromosome
• Plasmid – double-stranded DNA molecule in a ring; can be transferred from one bacterium to another. Commonly used in genetic engineering
• Endospores - Specialized “resting cells” formed by some Gram-positive bacteria such as Clostridium  and Bacillus. Formed when nutrients are depleted
• Reproduction of Prokaryotic Cell

  Asexual reproduction, usually by: Binary fission and Budding
• Binary fission - process results in the reproduction of a living prokaryotic cell by division into two parts which each have the potential to grow to the size of the original cell
• Budding - formation of a new organism by the protrusion of part of another organism