cell biology

• Plant cell


  • Nucleus
  • Mitochondria
  • Cell membrane
• Animal cell


  • Nucleus
  • Cytoplasm
  • Cell wall
• Cell wall


  • Strength
  • Protection
  • Support
• Cytoplasm


  • Site of chemical reactions
  • Site of respiration
  • Releases energy
• Eukaryotic cells


  Contain nucleus (plant/animal)
• Prokaryotic cells


  • No nucleus (bacteria)
  • Genetic info (DNA) stored in plasmid and chromosome floating in cytoplasm
• Plasmids


  • Small, circular loops of DNA found free in the cytoplasm
  • Control some cell activities
• Chromosomal DNA


  Controls most cell activity
• Flagellum


  Allows movement
• Ribosomes


  Found in cytoplasm
• Cell differentiation


  Process by which cells become specialised
• Most animal cells differentiate at an early stage in their life cycle
• Plant cells retain the ability to differentiate throughout their life
• Importance of cell differentiation


  • Allows production of different tissues/organs that perform various vital functions in human body
• Cell division in mature animals

  For repair/replacement of cells
• Changes a cell goes through as it differentiates


  Acquires different sub-cellular structures to enable it to carry out a certain function to become specialized
• Sperm cell


  • Haploid nucleus - contains genetic info
  • Acrosome - contains enzymes that digest egg cell membrane
  • Tail - for movement
  • Mitochondria - provide energy
• Nerve cell


  • Long axon allows electrical impulses to be transmitted all over the body
  • Dendrites make lots of connections
  • Myelin sheath - insulator on axon to increase speed of neurotransmission
• Muscle cell


  • Mitochondria - provide energy for contraction
  • Arrangement of protein filaments - allows them to slide over each other to produce contraction
• Root hair cell


  • Large surface area - absorb lots of water
  • Thin walls - allow water to pass through easily
• Xylem cells


  • Upper/lower margin between cells - provide continuous route for water to flow
  • Thick cell wall - strengthen structure, prevent collapsing
• Phloem cells


  • Sieve plates - allow dissolved sugars to move up and down
  • Companion cells - provide energy needed for active transport of substances
• Stem cells


  Unspecialised cells capable of differentiating into other cell types or self-renewal
• Adult stem cells


  • Found in specific parts of body (e.g. bone marrow)
  • Can differentiate into several cell types to replace damaged tissues
• Embryonic stem cells


  • Found in human embryos
  • Can differentiate into any type of specialised cell
• Meristem tissue in plants

  • Found in roots and shoots
  • Can differentiate into any type of cell
  • Can be used to clone plants
• Therapeutic cloning


  • An embryo is produced with the same genes as the patient
  • Stem cells from this embryo can be used for medical treatments
• Light microscope


  • Low resolution
  • 2D images only
  • Lower magnification
  • Can see cells, large organelles (nucleus)
  • Can see living samples
• Electron microscope


  • High resolution
  • 3D imaging possible
  • Higher magnification
  • Can see smaller structures (mitochondria)
  • Can't see living samples (would kill them)
• Light microscope advantages


  • Easy to use
  • Inexpensive
• Light microscope disadvantages


  • Limited resolution
  • 2D images only
  • Lower magnification
• Electron microscope advantages


  • Higher resolution
  • 3D imaging possible
  • Greater magnification
• Electron microscope disadvantages


  • Expensive
  • Require training to use
• Magnification


  Total magnification = eyepiece lens x objective lens
• Making a slide


  1. Thin layer of cells so light can pass through

  2. Add stain so cells can be observed

  3. Add cover slip to flatten cells
• Viewing a slide


  1. Place slide on stage and hold down with clips

  2. Turn objective lens to x4

  3. Use coarse focusing wheel to raise stage

  4. Use fine focusing wheel to bring sample into focus

  5. Turn to x10, repeat