Detailed

• 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 used to show multiples of units

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

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Organelles found only in plant cells


  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Components of bacterial cells


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


  The process where cells undergo differentiation to become suited to a specific 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 acquire new structures and functions to become specialized cells
• In animals, most cells differentiate early and lose the ability, while in plants many cells retain the 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 an object

  Size of image / magnification = size of object
• Standard form


  A way to represent very large or small numbers by multiplying by a power of 10
• Culture medium


  Contains carbohydrates, minerals, proteins and vitamins to grow microorganisms
• Growing microorganisms in nutrient broth

  Make a suspension of bacteria, mix with sterile nutrient broth, stopper with cotton wool, shake regularly
• Standard form


  Multiplying a certain number by a power of 10 to make it bigger or smaller, with the 'number' being between 1 and 10
• 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
• Components of culture medium

  • Carbohydrates
  • Minerals
  • Proteins
  • Vitamins
• Growing microorganisms in nutrient broth

  1. Make suspension of bacteria

  2. Mix with sterile nutrient broth

  3. Stopper flask with cotton wool

  4. Shake regularly
• 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
• Calculating number of bacteria after growth period

  1. Bacteria at beginning x 2^(number of divisions) = bacteria at end

  2. Number of divisions = time left / mean division time
• Inhibition zone


  Clear area around antibiotic disc where bacteria have died
• Testing antibiotic effectiveness


  1. Soak paper discs in different antibiotics and place on agar plate with bacteria

  2. Include control disc with sterile water

  3. Measure size of inhibition zones after 2 days incubation at 25°C
• Calculating cross-sectional areas of colonies or inhibition zones involves using the formula πr^2
• Chromosomes


  Contain coils of DNA and carry genes
• There are 23 pairs of chromosomes in each body cell, resulting in 46 chromosomes total
• Sex cells (gametes) have half the number of chromosomes, 23 in total
• Cell cycle and mitosis

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

  2. Mitosis: chromosomes line up at equator, cell fibres pull them to opposite sides

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