Cell Theory & Membranes


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Cell Theory & Membranes

  1. 1. The Cell Theory 1. All living things are made up of one or more cells 2. Cells are the basic unit of structure and function 3. All cells come from pre-existing cells 4. Cells contain the hereditary information which is passed from cell to “daughter” cell during cell division 5. All cells are basically the same in chemical composition
  2. 2. The Cell Membrane: Gatekeeper of the Cell How do the “approved” molecules get across the membrane? The cell membrane regulates what molecules can and cannot go into the cell
  3. 3. Getting Across the Membrane How do approved molecules get across the membrane? By transport! There are two types: <ul><li>Passive transport (requires no energy)‏ </li></ul><ul><li>a) Simple diffusion </li></ul><ul><li>b) Facilitated diffusion </li></ul>2. Active transport (requires energy)‏
  4. 4. Diffusion Movement of molecules from areas of high concentration to areas of low concentration Movement continues until equilibrium is reached! Then there is no more NET movement of molecules.
  5. 5. Simple Diffusion (type of passive transport)‏ Movement of molecules across a membrane from areas of high concentration to areas of low concentration
  6. 6. Dialysis Bag Diffusion Experiment
  7. 7. Osmosis Osmosis is the simple diffusion of water molecules! Water moves from High water concentration to Low water concentration. SO, water moves from Low solute concentration to High solute concentration
  8. 8. Hypertonic hyper = above Hypotonic hypo = under Isotonic iso = equal When comparing the solute concentration between two solutions, you should use the following terms
  9. 9. Hypertonicity
  10. 10. Hypotonicity
  11. 11. Isotonicity
  12. 13. December 7, 2007 Bell-work: You place a cell containing 0.5 grams of solutes in a solution containing 0.7 grams of solutes. The cell membrane is not permeable to the solutes.   1. The cell is __________ to its environment (hypertonic/hypotonic/isotonic)‏ 2. The environment is _______ to the cell. (hypertonic/hypotonic/isotonic)‏ 3. Will the solutes diffuse? If yes, in which direction (in/out)? 4. Will the water diffuse? If yes, in which direction (in/out)?
  13. 14. Facilitated Diffusion (type of passive transport)‏ Special protein channels in the membrane allow for the transport of molecules into the cell from areas of high concentration to low concentration
  14. 15. Active Transport Movement of substances AGAINST the concentration gradient From areas of low concentration to areas of high concentration REQUIRES ENERGY! Two ways: 1. Protein Pumps 2. Carriers (vesicles)‏
  15. 16. 1. Protein Pumps
  16. 17. 2. Vesicles Membrane-bound organelles that carry products or wastes into, out of, or throughout the cell
  17. 18. Endocytosis substances are brought into the cell Think of it as cellular eating and drinking! Amoeba “eating” some bacteria
  18. 19. Exocytosis substances are released from the cell
  19. 20. Endo- or Exo- cytosis Video
  20. 21. Picture Overview
  21. 22. Is it a Prokaryote or a Eukaryote?
  22. 23. Plants
  23. 25. Bacteria
  24. 26. Protist
  25. 27. Animals