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
• 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
  • 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 affects water movement
  • Mitochondria to provide energy for active transport of mineral ions
• Xylem cells


  • Lignin deposited to form hollow tubes for water/mineral transport
  • Lignin deposited in spirals to withstand 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
  • Maximum magnification of x2000 and resolving power of 200nm
• Electron microscope


  • Uses electrons instead of light to form image
  • Scanning type creates 3D images, transmission type creates 2D images of organelles
  • Magnification up to x2,000,000 and 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 and mix with sterile nutrient broth, stopper with cotton wool, shake regularly
• Growing microorganisms on agar plates

  Spread bacteria suspension on agar plate, seal and incubate
• 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
• Making an agar gel plate involves pouring hot sterilised agar jelly into a sterilised Petri dish, letting it cool and set, inoculating with a wire loop, and incubating
• Sterilisation


  Petri dishes and culture media must be sterilised before use, often by autoclave or UV light, to prevent contamination
• Inoculating loops


  Wire loops that are sterilised by passing through a flame to kill unwanted microorganisms
• Sealing Petri dish


  Lid should be sealed but not completely, to prevent airborne contamination while allowing oxygen entry
• Storing Petri dish


  Upside down to prevent condensation from the lid disrupting growth
• Incubation temperature


  25 degrees, to prevent growth of bacteria harmful to humans
• Testing antibiotic effectiveness


  Soak paper discs in antibiotics, place on agar plate with bacteria, measure inhibition zone after incubation
• Calculating cross-sectional areas of colonies or inhibition zones involves using the formula πr^2, where r is the radius