Cell Biology WHOLE TOPIC

• All living things are made of cells, which can either be prokaryotic or eukaryotic.
• Eukaryotic cells

  • Animal cells
  • Plant cells
• Prokaryotic cells

  • Bacterial cells
• Eukaryotic cells

  • Have a cell membrane
  • Cytoplasm
  • Nucleus containing DNA
• Prokaryotic cells

  • Have a cell wall
  • Cell membrane
  • Cytoplasm
  • Single circular strand of DNA and plasmids
• Organelle

  Structures in a cell that have different functions
• Cells are extremely small, and we can use orders of magnitude to understand how much bigger or smaller one is from another.
• Understanding orders of magnitude

  1. If an object is 10 times bigger than another then we say it is 10​1 ​times bigger.

  2. If an object is 1000 times bigger than another then we say it is 10​3​ times bigger.

  3. If an object is 10 times smaller than another then we say it is 10​-1 ​times smaller.
• Prefixes

  • Centi
  • Milli
  • Micro
  • Nano
• Prefix multipliers

  • Centi: 0.01
  • Milli: 0.001
  • Micro: 0.000, 001
  • Nano: 0.000, 000, 001
• The subcellular structures inside cells all have a specific function.
• Specialised cells in animals

  • Sperm cells
  • Nerve cells
  • Muscle cells
• Specialised cells in plants

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

  The process that involves the cell gaining new sub-cellular structures in order for it to be suited to its role.
• Sperm cells

  • Specialised to carry the male’s DNA to the egg cell
  • Streamlined head and long tail to aid swimming
  • Many mitochondria for energy
  • Acrosome has digestive enzymes
• Nerve cells

  • Specialised to transmit electrical signals quickly
  • Long axon for long distances
  • Lots of extensions (dendrites)
  • Nerve endings have many mitochondria
• Muscle cells

  • Specialised to contract quickly
  • Special proteins (myosin and actin)
  • Lots of mitochondria for energy
  • Can store glycogen
• Root hair cells

  • Specialised to take up water and mineral ions
  • Large surface area due to root hairs
  • Large permanent vacuole
  • Mitochondria for energy
• Xylem cells

  • Specialised to transport water and mineral ions
  • Become hollow and joined end-to-end
  • Lignin deposited in spirals
• Phloem cells

  • Specialised to carry products of photosynthesis
  • Cell walls form sieve plates
  • Energy supplied by companion cells
• In animals, almost all cells differentiate at an early stage and then lose this ability.
• In plants, many types of cells retain the ability to differentiate throughout life.
• The first cells of a cork were observed by Robert Hooke in 1665 using a light microscope.
• Light microscope

  • Has two lenses
  • Produces a magnified image
  • Maximum magnification of x2000
  • Resolving power of 200nm
• Electron microscope

  • Uses electrons to form an image
  • Magnification of up to x2,000,000
  • Resolving power of 10nm (SEM) and 0.2nm (TEM)
• Calculating size of an object

  Size of image/magnification = size of object
• Microorganisms are very small, so in order for scientists to study them they need to grow many of them in the lab using nutrients.
• Components of culture medium

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

  1. Make suspension of bacteria

  2. Mix with sterile nutrient broth

  3. Stopper flask with cotton wool

  4. Shake regularly for oxygen
• Making an agar gel plate


  1. Pour hot sterilised agar into Petri dish

  2. Leave to cool and set

  3. Spread microorganism over agar

  4. Tape lid and incubate
• Bacteria can multiply by binary fission as fast as every 20 minutes.
• Calculating number of bacteria

  Bacteria at beginning x 2 number of divisions = bacteria at end
• The nucleus contains your genetic information in the form of chromosomes, which contain coils of DNA.
• Gene

  A short section of DNA that codes for a protein and controls a characteristic.
• 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 in each gamete cell.
• Cell cycle


  A series of steps that the cell has to undergo in order to divide.
• To calculate cross-sectional areas (of colonies or inhibition zones), use the formula πr², where r is the radius of the circle.
• Chromosomes

  Structures that contain coils of DNA and carry genetic information
• Gene

  A short section of DNA that codes for a protein and controls a characteristic