biology topic 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
• 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
• 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 over long distances
  • 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 for contraction
  • Can store glycogen for respiration
• Root hair cells


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


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


  • Sieve plates allow movement of substances between cells
  • 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) to magnify and direct image to eye
• Light microscope


  • Maximum magnification of x2000
  • Resolving power of 200nm
• Electron microscope


  Uses electrons instead of light to form image, enabling view of sub-cellular structures
• Electron microscope


  • Scanning electron microscope creates 3D images, transmission electron microscope creates 2D images
  • Magnification up to x2,000,000
  • Resolving power of 10nm (SEM) and 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


  Multiplying a number by a power of 10 to represent very large or small numbers
• 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


  • Microorganisms are very small, so scientists need to grow many of them in the lab using nutrients
• Components of culture medium

  • Carbohydrates for energy
  • Minerals
  • Proteins
  • Vitamins
• Growing microorganisms in the lab

  1. In nutrient broth solution

  2. On an agar gel plate
• Steps for making an agar gel plate
• Autoclave


  An oven used to sterilise Petri dishes and culture media before use
• Reasons for sterilising equipment
• Reasons for sealing Petri dish lid
• Reason for storing Petri dish upside down
• Reason for incubating at 25 degrees
• Testing antibiotic effectiveness


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

  2. Leave plate for 2 days

  3. Measure zone of inhibition