02 the plasma membrane


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02 the plasma membrane

  1. 1. A View of the Cell  Cells maintain homeostasis  Depends on the movement of materials in and out of the cell  Nutrients, waste and ions  Two factors govern the movement of materials in and out of the cell  Diffusion  The plasma membrane
  2. 2. Diffusion  Diffusion is caused by the random motion of atoms and molecules  Types of motion: vibrational, rotational and translational  The diffusion of water through a membrane is called osmosis
  3. 3. Diffusion in a Cell  The direction a molecule travels depends on…  The concentration gradient  The function the molecule plays in cell metabolism  3 situations exist between cells and their environment based on concentration  Hypotonic  Hypertonic  Isotonic
  4. 4. Diffusion in a Cell
  5. 5. Diffusion in a Cell
  6. 6. The Plasma Membrane  The plasma membrane separates the cell from its environment and controls what passes through it  The fluid mosaic model  The plasma membrane has a dynamic – ever changing – structural composition  A phospholipid bilayer  Cholesterol  Proteins
  7. 7. Phospholipids
  8. 8. The Role of Cholesterol  Cholesterol  Rigidity  Fluidity  Cholesterol  Rigidity  Fluidity  Cholesterol helps to maintain the proper fluidity of the membrane in cases of extreme temperature change
  9. 9. The Role of Proteins  Transport proteins  Move needed substances or waste material through the membrane
  10. 10. Methods of Cellular Transport Passive Transport  Requires no cell energy  Diffusion  Osmosis Active Transport  Requires the cell to expend energy  Used to get necessary metabolic chemicals  Particles move against the concentration gradient or are too large to pass through transport proteins
  11. 11. Passive Transport – Facilitated Diffusion  Channel proteins (a type of transport protein) create a passage or channel through which molecules can pass
  12. 12. Active Transport  Carrier proteins (a type of transport protein) bind with a molecule and uses energy to move it against the concentration gradient
  13. 13. Active Transport  When a molecule is too large to pass through the membrane…  …cells can absorb them by engulfing them  Endocytosis  Ex/ White blood cells, feeding  …cells can excrete or secrete them  Exocytosis  Ex/removal of waste, release of cellular product (neurotransmitters, hormones, enzymes)
  14. 14. Endocytosis  To absorb a large molecule (or organism!) a cell can…  …completely engulf it  Phagocytosis  https://www.youtube.com/watch?v=aWItglvTiLc
  15. 15. Endocytosis  To absorb a large molecule a cell can…  …make a small pocket (called a vesicle) out of the membrane to store it  Pinocytosis
  16. 16. Exocytosis  When a cell directs the contents of a vesicle out of the membrane into the extracellular space  Waste = excretion  Products = secretion