26 ch05cellsoverview2007


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  • Why organelles? There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions. Organelles as specialized structures An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move. Organelles as Containers Nothing ever invented by man is as complex as a living cell. At any one time hundreds of incompatible chemical reactions may be occurring in a cell. If the cell contained a uniform mixture of all the chemicals it would not be able to survive. Organelles surrounded by membranes act as individual compartments for these chemical reactions. An example of the second type of organelle is the lysosome. This structure contains digestive enzymes, these enzymes if allowed to float free in the cell would kill it. Organelle membranes as sites for chemical reactions An example of the third type of organelle is the chloroplast. The molecules that conduct the light reactions of photosynthesis are found embedded in the membranes of the chloroplast.
  • lysosomes create a space where cell can digest macromolecules safely rupturing a few lysosomes has little impact on a cell (pH of cytosol affects functionality of the lysosomal enzymes), but massive leakage from lysosomes can destroy cell why evolve digestive enzymes which function at pH so different from cytosol? digestive enzymes won’t function well if leak into cytosol = most times don’t want to digest yourself! low pH = acid environment cause oxidation (removing electrons) & promotes hydrolysis
  • Feedback mechanism There are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes. Brown spots on leaves too. Virus infected plant cell auto-destructs and even cells around it to wall off virus.
  • 26 ch05cellsoverview2007

    1. 1. AP Biology 2007-2008 Tour of the Cell
    2. 2. AP Biology Prokaryote bacteria cells Prokaryote bacteria cells Types of cells Eukaryote animal cells Eukaryote animal cells Eukaryote plant cells Eukaryote plant cells
    3. 3. AP Biology Why organelles?  Specialized structures  specialized functions  cilia or flagella for locomotion  Containers  partition cell into compartments  create different local environments  separate pH, or concentration of materials  distinct & incompatible functions  lysosome & its digestive enzymes  Membranes as sites for chemical reactions  unique combinations of lipids & proteins  embedded enzymes & reaction centers  chloroplasts & mitochondria mitochondria chloroplast Golgi ER
    4. 4. AP Biology Cells gotta live!  What jobs do cells have to do?  building proteins  proteins control every cell function  make energy  for daily life  for growth  build more cells  growth  reproduction  repair
    5. 5. AP Biology DNADNA Why study protein production? cellscells proteinsproteins organismorganism Repeat after me… DNA gets the glory, but Proteins do all the work!
    6. 6. AP Biology Building Proteins  Organelles involved  nucleus  ribosomes  endoplasmic reticulum (ER)  Golgi apparatus  vesicles nucleus ribosome ER Golgi apparatus vesicles The Protein Assembly Line
    7. 7. AP Biology DNA RNA ribosomes endoplasmic reticulum vesicle Golgi apparatus vesicle protein on its way! protein finished protein Making Proteins TO: TO: TO: TO: nucleus TO:
    8. 8. AP Biology proteins transport vesicle Golgi apparatus vesicle smooth ER rough ER nuclear pore nucleus ribosome cell membrane protein secreted cytoplasm Making proteinsPutting it together…
    9. 9. AP Biology Cells gotta live!  What jobs do cells have to do?  make proteins  proteins control every cell function  make energy  for daily life  for growth  build more cells  growth  reproduction  repair ATP
    10. 10. AP Biology Cells need power!  Making energy  take in food & digest it  take in oxygen (O2)  make ATP  remove waste ATP
    11. 11. AP Biology Lysosomes  Function  little “stomach” of the cell  digests macromolecules  “clean up crew” of the cell  cleans up broken down organelles  Structure  vesicles of digestive enzymes only in animal cellsonly in animal cells Christian de Duve 1960 | 1974 Where old organelles go to die!
    12. 12. AP Biology Lysosomal enzymes  Lysosomal enzymes work best at pH 5  organelle creates custom pH  how?  proteins in lysosomal membrane pump H+ ions from the cytosol into lysosome  why?  enzymes are very sensitive to pH  why?  enzymes are proteins — pH affects structure  why is this an adaptation: digestive enzymes which function at pH different from cytosol?  digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself!
    13. 13. AP Biology But sometimes cells need to die…  Lysosomes can be used to kill cells when they are supposed to be destroyed  some cells have to die for proper development in an organism  apoptosis  “auto-destruct” process  lysosomes break open & kill cell  ex: tadpole tail gets re-absorbed when it turns into a frog  ex: loss of webbing between your fingers during fetal development  ex: self-destruct of cancerous cell
    14. 14. AP Biology Fetal development 15 weeks 6 weeks syndactyly
    15. 15. AP Biology When things go wrong…  Diseases of lysosomes are often fatal  digestive enzyme not working in lysosome  picks up biomolecules, but can’t digest one  lysosomes fill up with undigested material  grow larger & larger until disrupts cell & organ function  lysosomal storage diseases  more than 40 known diseases  example: Tay-Sachs disease build up undigested fat in brain cells
    16. 16. AP Biology From food to making Energy  Cells must convert incoming energy to forms that they can use for work  mitochondria: from glucose to ATP  chloroplasts: from sunlight to ATP & carbohydrates  ATP = immediate energy  carbohydrates = stored energy + ATP ATP
    17. 17. AP Biology Mitochondria & Chloroplasts  Important to see the similarities  transform energy  generate ATP  double membranes = 2 membranes  semi-autonomous organelles  move, change shape, divide  internal ribosomes, DNA & enzymes Lynn Margulis U of M, Amherst
    18. 18. AP Biology Membrane-bound Enzymes glucose + oxygen → carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP→+ + +
    19. 19. AP Biology Membrane-bound Enzymes + water + energy → glucose + oxygencarbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy →+ ++
    20. 20. AP Biology Mitochondria are everywhere!! animal cellsanimal cells plant cellsplant cells
    21. 21. AP Biology Cells gotta live!  What jobs do cells have to do?  building proteins  proteins control every cell function  make energy  for daily life  for growth  build more cells  growth  reproduction  repair
    22. 22. AP Biology Cytoskeleton  Function  structural support  maintains shape of cell  provides anchorage for organelles  protein fibers  microfilaments, intermediate filaments, microtubules  motility  cell locomotion  cilia, flagella, etc.  regulation  organizes structures & activities of cell
    23. 23. AP Biology  actin  microtubule  nuclei Cytoskeleton
    24. 24. AP Biology Centrioles  Cell division  in animal cells, pair of centrioles organize microtubules  guide chromosomes in mitosis