topic 1 - cell biology

• Eukaryotes


  Cells that have a nucleus and membrane-bound organelles
• Prokaryotes


  Cells that lack a nucleus and membrane-bound organelles
• Components of animal and plant cells

  • Cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• Components of bacterial cells

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• Orders of magnitude


  A way to understand how much bigger or smaller one object is compared to another
• Prefixes to show multiples of units

  • Centi (0.01)
  • Milli (0.001)
  • Micro (0.000,001)
  • Nano (0.000,000,001)
• Structures in animal and plant cells

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Additional structures in plant cells

  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Structures in bacterial cells

  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Single circular strand of DNA
  • Plasmids
• Cell specialization


  The process where cells gain new sub-cellular structures to be suited to their role
• Specialized animal cells


  • Sperm cells
  • Nerve cells
  • Muscle cells
• Specialized plant cells


  • Root hair cells
  • Xylem cells
  • Phloem cells
• Cell differentiation


  The process where stem cells switch on/off genes to become specialized cells
• In animals, most cells differentiate early and lose ability to differentiate, but some retain ability as adult stem cells
• In plants, many cell types retain ability to differentiate throughout life
• Light microscope


  Has two lenses (objective and eyepiece), magnifies up to x2000, resolving power of 200nm
• Electron microscope


  Uses electrons instead of light, magnifies up to x2,000,000, resolving power of 10nm (SEM) and 0.2nm (TEM)
• Calculating magnification


  Magnification of eyepiece lens x magnification of objective lens
• Calculating size of object

  Size of image / magnification = size of object
• Culture medium


  Contains carbohydrates, minerals, proteins and vitamins to grow microorganisms
• Standard form examples


  • 1.5 x 10^-5 = 0.000015
  • 3.4 x 10^3 = 3400
• Culturing microorganisms


  Growing many microorganisms in the lab using nutrients
• Growing microorganisms on agar gel plate

  1. Pour hot sterilised agar jelly into sterilised Petri dish

  2. Allow to cool and set

  3. Inoculate with microorganism using sterilised loop

  4. Seal plate and incubate
• Reasons for steps in culturing microorganisms

  • Sterilise Petri dishes and culture media to prevent contamination
  • Sterilise inoculating loops to kill unwanted microorganisms
  • Seal plate but not completely to allow oxygen
  • Store plate upside down to prevent condensation
  • Incubate at 25°C to prevent growth of harmful bacteria
• Binary fission


  One cell splitting into two
• Bacteria can multiply by binary fission as fast as every 20 minutes
• The number of bacteria at the end can be very large, so it is common to use standard form
• Testing antibiotics on bacteria


  1. Soak paper discs in different antibiotics

  2. Place discs on agar plate with bacteria

  3. Leave plate at 25°C for 2 days

  4. Measure size of inhibition zone around discs
• Inhibition zone


  The clear area around an antibiotic disc where bacteria have died
• The bigger the inhibition zone, the more effective the antibiotic
• Chromosomes


  Contain coils of DNA and carry genes
• There are 23 pairs of chromosomes in each body cell, and 23 chromosomes in each sex cell
• Cell cycle and mitosis

  1. Interphase: cell grows, organelles increase, DNA replicates

  2. Mitosis: chromosomes line up and are pulled to opposite sides

  3. Cytokinesis: cytoplasm and cell membrane divide to form two daughter cells
• Mitosis


  The stage of the cell cycle when the cell divides
• Importance of mitosis


  • Growth and development
  • Replacing damaged cells
  • Asexual reproduction
• Stem cells


  Undifferentiated cells that can divide to produce more similar cells, some of which can differentiate
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Meristems in plants
• Therapeutic cloning


  Producing an embryo with the same genes as the patient to obtain stem cells for treatment
• Diffusion


  The spreading out of particles in a solution or gas, resulting in net movement from higher to lower concentration
• Diffusion is passive and does not require energy