Cell Fractionation

• Plasmids


  small circular loops of DNA
• Converting between the values for logarithms growth and exponential growth


  • 10^of log10 value for that generation = exponential value
• Cell wall made up of murein
• Environmental variables and how they increase cell growth rate:

  increased glucose concentration=increased respiration

  increased oxygen concentration=increased respiration

  increased temperature=increased enzyme activity

  increased phosphate concentration=increased ATP/RNA/DNA

  increased nucleotide concentration=increased DNA synthesis
• Replication of Bacteria:

  process is called binary fission

  DNA replicates

  plasmids replicate

  cytoplasm divides to two daughter cells

  each new cell has a single copy of circular DNA and a variable number of plasmids
• Fractionation and Ultracentrifugation:

  to isolate organelles so they can be studied

  the property used to separate the organelles is density
• Steps for cell fractionation:

  1. Tissue is chopped in an ice-cold, isotonic, buffer solution

  2. Cell is homogenized to break open cells and release organelles

  3. Suspension is filtered to remove debris

  4. Mixture is centrifuged slowly for a short time, dense cell contents settle into a pellet called a fraction

  5. The liquid layer on top (supernatant) is poured into a fresh tube, leaving the sediment behind, which contains nuclei

  6. Centrifuge supernatant at high speed and for longer to separate a fraction containing less dense organelles in the pellet (e.g., mitochondria, chloroplast)

  7. Centrifuge supernatant even faster and longer to obtain a pellet containing less dense organelles (e.g., ribosomes)

  8. Use a transmission microscope to study the detail in the organelles, and use scanning for a 3D image