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• Eukaryotes

  Animals and plants
• Animal cell

  • Nucleus
  • Cytoplasm
  • Cell membrane
• Plant cell

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Sap vacuole
  • Chloroplast
• Prokaryotes

  Usually bacterial cells with no nucleus or subcellular structures with membranes
• Prokaryotic cells have circular DNA and plasmids
• Approximate cell sizes: Animal 10 micrometers, Plant 50 micrometers, Prokaryote 5 micrometers
• Cell differentiation


  The process by which undifferentiated cells become specialised cells
• Specialised animal cells


  • Nerve cells
  • Muscle cells
  • Sperm cells
• Specialised plant cells


  • Xylem
  • Phloem
  • Root hair cells
• Nerve cell


  • Cell body
  • Dendrites
  • Axon
  • Insulating sheath
  • Axon terminals
• Sperm cell

  • Mid piece with mitochondria
  • Tail
  • Acrosome
  • Nucleus
• Muscle cell


  • Fibers that can shorten
  • Mitochondria
  • Glycogen store
• Xylem cell


  • No end plates
  • No cytoplasm
  • Rings of lignin
• Phloem cell


  • Very little cytoplasm
  • End plates with pores
  • Companion cells
• Root hair cell


  • Large surface area
  • Many mitochondria
• Simple microscope

  Low magnification and low resolving power
• Electron microscope

  High magnification and high resolving power
• Magnification calculation


  Size of image / Size of real object
• Cell cycle

  Stage 1: Cell growth and DNA replication

  Stage 2: Mitosis - chromosomes line up and separate

  Stage 3: Cytoplasm and cell membrane divide
• Embryonic stem cells


  Undifferentiated cells from the early embryo that can develop into any cell type
• Cell growth and division

  1. Cell grows and increases number of subcellular structures

  2. DNA replicates to form two copies of each chromosome

  3. Chromosomes line up along center and are pulled to each end of cell

  4. Cytoplasm and cell membranes divide to form two genetically identical cells
• Mitosis


  The process of cell division described above
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Plant stem cells (meristem tissue)
• Embryonic stem cells


  • Undifferentiated
  • Can be cloned
  • Can differentiate into most other cell types
• Adult stem cells


  • Found in bone marrow
  • Can differentiate into many cell types, mainly blood cells
• Plant stem cells


  • Found in meristem tissue in root and shoot tips
  • Can differentiate into any plant cell
• Therapeutic cloning


  1. Patient body cell nucleus removed and inserted into empty human egg cell

  2. Cloned to produce stem cells

  3. Stem cells differentiated to make specialized cells/tissues for treatment
• Diffusion


  Spreading out of particles in a solution or gas, with net movement from higher to lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Active transport


  Movement of particles from lower to higher concentration, requires energy
• Examples of diffusion in living things

  • Oxygen diffusing into cells from blood
  • Carbon dioxide diffusing out of cells into blood
  • Urea diffusing out of cells
• Examples of active transport in living things

  • Sugar absorption in small intestine
  • Mineral ion absorption in root hair cells
• Surface area to volume ratio

  • Measure of how much surface area an organism has relative to its volume
  • Smaller organisms have higher ratio, allowing sufficient transport of molecules
• Adaptations for exchange systems in larger organisms

  • Villi and microvilli in small intestine to increase surface area
  • Thin walls for short diffusion distance
  • Many mitochondria for active transport energy
  • Good blood supply to maintain concentration gradient
• Adaptations for gas exchange in lungs

  • Many alveoli to increase surface area
  • Thin alveolar walls for short diffusion distance
  • Good blood supply to maintain concentration gradient
  • Ventilation to maintain oxygen concentration
• Adaptations for gas exchange in leaves

  • Flat, thin shape to increase surface area
  • Air spaces between cells to increase diffusion rate
  • Stomata that can open/close to regulate gas exchange
• Adaptations for gas exchange in fish gills

  • Many gill filaments to increase surface area
  • Thin capillary walls for short diffusion distance
  • Good blood supply to maintain concentration gradient
  • Fresh water flow over filaments to maintain oxygen concentration
• Osmosis

  Diffusion of water from a dilute to a concentrated solution through a partially permeable membrane
• Osmosis in plant cells


  Water moves into the cell, making it turgid
• Osmosis in root hair cells


  Water moves into the cell from the dilute soil solution