Biology Chapter 1

• 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
• Organelles


  Structures in a cell that have different functions
• Orders of magnitude


  Used to understand how much bigger or smaller one object is from another
• Prefixes

  • 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
• Structures only in plant cells

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

  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Single circular strand of DNA
  • Plasmids
• Sperm cells

  • Streamlined head and long tail to aid swimming
  • Many mitochondria to supply energy
  • Acrosome with digestive enzymes to break down egg cell membrane
• Nerve cells

  • Long axon to transmit impulses
  • Many dendrites to form branched connections
  • Mitochondria to supply energy for neurotransmitter production
• Muscle cells

  • Proteins (myosin and actin) that slide over each other to cause contraction
  • Many mitochondria to provide energy
  • Can store glycogen for respiration
• Root hair cells

  • Large surface area from root hairs
  • Large permanent vacuole
  • Mitochondria to provide energy for active transport of mineral ions
• Xylem cells

  • Lignin deposited to form hollow tubes
  • Lignin deposited in spirals to withstand water pressure
• Phloem cells

  • Sieve plates allow movement of substances
  • Rely on mitochondria in companion cells for energy
• Cell differentiation

  Process where stem cells acquire new sub-cellular structures to become specialised cells
• In animals, most cells differentiate early and lose ability to differentiate further
• In plants, many cell types retain ability to differentiate throughout life
• Light microscope

  Has two lenses (objective and eyepiece), illuminated from underneath, maximum magnification of x2000 and resolving power of 200nm
• Electron microscope

  Uses electrons instead of light, can achieve magnification up to x2,000,000 and resolving power of 0.2nm (TEM)
• Calculating magnification of light microscope

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

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

  Expressing very large or small numbers by multiplying by a power of 10, with the 'number' between 1 and 10
• Culture medium

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

  Make 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 to provide oxygen
• 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 sterilisation


  • Prevents contamination with other microorganisms
  • Prevents competition for nutrients and space
  • Prevents introduction of harmful microorganisms
• Reasons for sealing plate

  • Stops airborne microorganisms from contaminating culture
  • Prevents anaerobic bacteria growing due to lack of oxygen
• Reasons for storing plate upside down

  • Prevents condensation from lid disrupting growth
• Reasons for incubating at 25°C

  • Prevents growth of bacteria harmful to humans
• Testing antibiotic effectiveness


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

  2. Leave plate to incubate

  3. Measure size of inhibition zone around discs
• Bigger inhibition zone indicates more effective antibiotic
• Inhibition zone


  Clear area around antibiotic disc where bacteria have died
• To calculate cross-sectional areas, use the formula πr^2