unit 2

• How prokaryotic cells form new cells

  Binary fission
• Types of cell division

  • Mitosis
  • Meiosis
• Role of cell surface membrane

  Selectively permeable to control the exchange of material
• Molecules found in plasma membranes

  • Phospholipids
  • Proteins
• Cells with internal membranes


  Eukaryotic cells
• Role of the nucleus

  Stores DNA in the form of chromatin
• Role of the nucleolus

  Makes ribosomes
• Role of chloroplasts

  Absorb light energy for photosynthesis
• Location of chloroplasts

  Plants and algae
• Role of Golgi apparatus

  Modifies and packages proteins, adds carbohydrates to form glycoproteins
• Role of lysosomes

  Contain lysosymes which hydrolyse pathogens or worn out organelles
• Difference between RER and SER

  Rough contains ribosomes on surface, smooth does not
• Role of the RER


  Transports proteins made at ribosomes
• Role of the SER

  Synthesise, store and secrete lipids
• Cells with a cell wall

  Prokaryotes and some eukaryotes - plants, fungi
• Cells with microvilli

  Epithelial cells of the ileum
• Role of the cell vacuole

  Storage of water/sugars needed for growth, waste disposal and turgidity
• Differences between prokaryotic and eukaryotic cells

  • Linear DNA vs circular DNA
  • Nucleus vs no nucleus
  • Membrane bound organelles vs none (like mitochondria, chloroplast, golgi body)
  • 80S ribosomes vs 70S ribosomes
• Cells with plasmids

  Prokaryotes = bacteria
• Stain used to locate starch grains in a plant cell

  Iodine
• Calculation of magnification

  Magnification = image size / actual size
• Resolution

  Minimum distance two objects can be seen to be distinct from one another
• Reason electron microscope has greater resolving power than optical microscope

  Shorter wavelength of electrons
• Artefact in microscopy

  Something introduced to the image during preparation, excess stain for example, which is not naturally there
• Purpose of cell fractionation


  Separate out organelles for study
• Homogenisation

  Blending or breaking open cells to release contents
• Properties of solution used to homogenise tissue


  • Isotonic
  • Ice cold
  • pH buffered
• Reason for filtering after homogenisation

  Remove any debris which may have similar mass to organelles
• Reason organelles separate out during centrifugation

  Based on mass - heavier will go to bottom at lower speeds
• Material left at bottom of tube after centrifugation

  Pellet - heaviest organelles first
• Order organelles separate out

  • Nucleus
  • Mitochondria/chloroplast
  • Lysosomes
  • Endoplasmic reticulum
  • Ribosomes
• Stage of cell cycle DNA replication occurs


  Interphase - S phase
• Stages of mitosis

  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Cytokinesis

  Separation of the cell membranes to create two daughter cells
• Cause of tumours and cancers

  Uncontrolled mitosis
• What many cancer treatments target

  DNA synthesis in interphase of rapidly dividing cells
• Viruses do not undergo cell division
• Reason root tips used to study mitosis

  Lots of mitosis occurring in growing tip, more likely to see each stage
• Calculation of mitotic index

  Number of cells in mitosis/total number of cells observed
• Binary fission

  Bacteria dividing from one parent cell to two daughter cells