cell biology

• Eukaryotic cells


  Cells that contain their genetic material enclosed in a nucleus
• Eukaryotic cells


  • Contain a nucleus
  • Contain a cell membrane
  • Contain cytoplasm
• Prokaryotic cells


  Cells where the genetic material is not enclosed in a nucleus
• Prokaryotic cells


  • Do not have a nucleus
  • Have a cell membrane
  • Have a cell wall
  • Contain cytoplasm
  • May have plasmids
• Prokaryotic cells


  Are much smaller than eukaryotic cells
• Order of magnitude


  A way to compare the approximate size of different objects
• Objects around the same order of magnitude

  • Apple and orange
• Pineapple compared to lemon

  Pineapple is around 10 times larger, so it is 1 order of magnitude larger
• How to determine order of magnitude

  Count the number of zeros - each zero represents 1 order of magnitude
• Calculating order of magnitude difference

  Divide the larger measurement by the smaller measurement to get the number of times larger

  2. The number of zeros in this result gives the order of magnitude difference
• Animals are eukaryotes, their genetic material (DNA) is enclosed in a nucleus
• Nucleus


  Encloses the genetic material
• Cytoplasm


  Watery solution where chemical reactions take place, including the first stage of respiration
• Cell membrane


  Controls the molecules that can enter and leave the cell
• Mitochondria


  • Where aerobic respiration takes place
• Ribosomes


  • Sites of protein synthesis, proteins carry out many functions like enzymes
• Mitochondria and ribosomes are too small to be seen using a light microscope, an electron microscope is required
• Specialized animal cells


  Cells that have adaptations which help them carry out a particular function
• Differentiation


  When cells become specialized
• Sperm cells


  • Long tail to swim to ovum
  • Packed with mitochondria to provide energy for swimming
  • Contain enzymes to digest outer layer of ovum
• Fertilization


  The process where the genetic information of the ovum and sperm combine
• Nerve cells

  • Long axon to transmit electrical impulses
  • Axon covered in myelin to insulate and speed up transmission
  • Cell body has dendrites to increase surface area for connections
• Muscle cells


  • Contain protein fibers that can contract to shorten the cell
  • Packed with mitochondria to provide energy for contraction
• Muscle cells work together to form muscle tissue
• Differentiation


  The process where cells become specialized
• Root hair cells


  • Increase the surface area of the root to absorb water and dissolved minerals more effectively
  • Do not contain chloroplasts
• Xylem cells


  • Have very thick walls containing lignin to provide support
  • Have no internal structures like nucleus, cytoplasm, vacuole or chloroplasts to allow easy flow of water and dissolved minerals
• Phloem cells


  • Consist of two types: phloem vessel cells with no nucleus and limited cytoplasm, and companion cells with mitochondria to provide energy to the phloem vessel cells
  • Have pores called sieve plates in the end walls to allow glucose to move through
• Xylem cells form long tubes that carry water and dissolved minerals from the roots to the leaves
• Phloem tubes carry dissolved sugars up and down the plant
• Optical microscope


  Used to look at cells on a prepared microscope slide
• Optical microscope


  • Has a stage to place the microscope slide
  • Has a light source (lamp or mirror) to illuminate the slide
  • Has objective lenses with different magnifications (4x, 10x, 40x)
  • Has an eyepiece lens with 10x magnification
  • Has coarse and fine focusing dials
• Using an optical microscope to view a prepared slide


  1. Place slide on stage and secure with clips

  2. Select lowest power (4x) objective lens

  3. Slowly turn coarse focus dial to lower lens until it almost touches slide

  4. Look through eyepiece and turn coarse focus dial to bring cells into focus

  5. Use fine focus dial to sharpen focus

  6. Calculate total magnification by multiplying eyepiece (10x) and objective (4x, 10x, 40x) lens magnifications
• What you might see under an optical microscope

  • Animal cells: nucleus, cytoplasm, cell membrane, possible mitochondria
  • Plant cells: cell wall, cytoplasm, nucleus, possible vacuole and chloroplasts
• An optical microscope can only show limited detail, cannot see organelles like ribosomes
• Drawing of cells should include a magnification scale
• Optical microscope


  Used to look at cells on a prepared microscope slide
• Optical microscope


  • Has a stage to place the microscope slide
  • Has a light source (lamp or mirror) to illuminate the slide
  • Has objective lenses with different magnifications (4x, 10x, 40x)
  • Has an eyepiece lens with 10x magnification
  • Has coarse and fine focusing dials
• Using an optical microscope to view a prepared slide


  1. Place slide on stage and secure with clips

  2. Select lowest power (4x) objective lens

  3. Slowly turn coarse focus dial to lower lens near slide

  4. Look through eyepiece and turn coarse focus dial to bring cells into focus

  5. Use fine focus dial to sharpen focus

  6. Calculate total magnification by multiplying objective and eyepiece lens magnifications
• What you might see under an optical microscope

  • Animal cells: nucleus, cytoplasm, cell membrane, possible mitochondria
  • Plant cells: cell wall, cytoplasm, nucleus, possible vacuole and chloroplasts