B1 - 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 specialisation


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


  • Sperm cells
  • Nerve cells
  • Muscle cells
• Specialised plant cells


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


  The process where stem cells switch on/off genes to produce different proteins and acquire new sub-cellular structures
• In animals, most cells differentiate early and lose ability to differentiate further. In plants, many cells retain ability to differentiate throughout life.
• Light microscope

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

  Uses electrons instead of light, two types (scanning and transmission), max magnification x2,000,000, resolving power 10nm (SEM) and 0.2nm (TEM)
• Magnification calculation

  Magnification of eyepiece lens x magnification of objective lens
• Size calculation

  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, with the 'number' between 1 and 10
• Culture medium

  Contains carbohydrates, minerals, proteins and vitamins to grow microorganisms
• 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 plates

  1. Pour sterile agar into petri dish

  2. Allow to set

  3. Spread bacteria suspension on surface

  4. Incubate at optimum temperature
• 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
• If Petri dishes and culture media are not sterilised

  They are likely to be contaminated with other microorganisms
• If the lid of the Petri dish is sealed all the way around

  Harmful anaerobic bacteria would grow due to lack of oxygen
• If the culture is incubated at higher temperatures near 37 degrees


  Bacteria that could be harmful to humans would be more likely to grow
• The zone of inhibition can be measured to determine the effectiveness of an antibiotic
• Chromosomes


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

  1. Interphase

  2. Mitosis

  3. Cytokinesis
• Importance of cell division by mitosis


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

  Undifferentiated cells that can undergo division to produce many more similar cells, some of which will differentiate to have different functions
• Types of stem cells

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