Cell Biology

• Prokaryotic cell


  • Typical structures: Cytoplasm, cell membrane, cell wall, bacterial DNA, plasmid DNA
  • Cytoplasm is where chemical processes occur
  • Cell wall strengthens the cell
  • Bacterial DNA controls function and synthesizes proteins
  • Plasmid DNA is used as a vector in genetic modification
• Differences between prokaryotic and eukaryotic cells


  • Prokaryotic cells are smaller than eukaryotic cells
  • Prokaryotic cells contain genetic material free in the cytoplasm
  • Prokaryotic cells have plasmids
• Similarities between prokaryotic and eukaryotic cells


  • Both have cytoplasm
  • Both have cell membranes
  • Both have genetic material
• Mitochondria


  • Cells require energy to function
  • Mitochondria is the site of respiration
  • Energy is released in respiration
• Ribosomes


  Synthesize proteins by producing them from amino acids
• Nucleus


  • Controls the activities of the cell
  • Contains the genetic material
• Cells without a nucleus


  • Red blood cells
  • Sperm cells
  • Bacterial cells
  • Prokaryotic cells
• Differentiation


  How cells change over time to become specialized for a specific function
• Animal stem cells


  Differentiate early in their life (embryonic stem cells)
• Plant stem cells


  • Can differentiate at any time throughout their life (meristematic stem cells)
  • Grouped together in structures called meristems
  • Used for growth and repair
• Required practical: Microscopy


  1. Equipment needed: Microscope, glass slide, scalpel, iodine

  2. Cut section of onion peel, place epidermis on slide without air bubbles

  3. Stain specimen with iodine to make subcellular structures clearer

  4. Gently lower cover slip, soak excess iodine

  5. Turn on power, place slide on stage, use lowest objective lens, adjust focus
• Reasons why a student couldn't see clearly through the microscope
• Magnification


  The ability to make an object appear larger than it actually is
• Resolving power/resolution


  The ability to distinguish between two closely spaced objects
• Light microscope


  • Small and portable
  • Low cost
  • Easy to use
• Electron microscope


  • Higher resolution
  • Higher magnification
  • Larger
  • Not portable
  • High cost
  • Requires specialists to use
• Electrons have a shorter wavelength than light


  They have a higher ability to see small things, meaning higher resolving power
• Mitosis


  The process of cell division that produces two genetically identical daughter cells
• Mitosis is important for multicellular organisms because it repairs cells, replaces cells, and forms clones of the original cell to keep favourable characteristics
• Stages of mitosis


  1. Chromosomes/DNA duplicate

  2. One set of chromosomes pulled to each end of the cell

  3. Cytoplasm and cell membrane divide to form two identical daughter cells
• Mitosis produces two genetically identical cells
• Diffusion


  The net movement of particles from an area of higher concentration to an area of lower concentration, down the concentration gradient
• The greater the difference in concentration


  The faster the rate of diffusion
• Adaptations for transport in cells - Plants

  • Root hair cells have no chloroplasts to increase surface area
  • Xylem and phloem for transport
• Adaptations for transport in cells - Animals


  • Small intestine has villi to increase surface area
  • Thin walls for rapid diffusion
  • Long length for more time for absorption
  • Lungs have alveoli to increase surface area
  • Good blood supply
  • Gills have filaments and lamellae to increase surface area
  • Thin, elastic walls
• Lower oxygen concentration in water


  • Shallower oxygen concentration gradient
  • Less oxygen can diffuse into gills
  • Less aerobic respiration
  • Less energy released
  • Lower metabolism
  • Axolotl may die
• Required practical for osmosis: Use a cork borer to cut potato cylinders of equal diameter, use a scalpel to cut to equal length, measure and record length and mass, add to different molar solutions, leave overnight, re-measure length and mass
• To determine the concentration of the solution inside an egg, the same process as the potato practical can be used
• Active transport of nitrate ions into root hair cells

  Energy is needed to move nitrate ions from lower concentration in soil to higher concentration in root