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Cell Membrane & The Ways Molecules Move

Cell Membrane & The Ways Molecules Move. I. Cell Membrane. 1) POLAR ends face INSIDE & OUTSIDE cell [where water is]. 2) NONPOLAR tails face each other inside bilayer [to avoid water]. Outside of cell. Carbohydrate chains. Proteins. Cell membrane. Protein channel. Inside

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Cell Membrane & The Ways Molecules Move

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  1. Cell Membrane&The Ways Molecules Move

  2. I. Cell Membrane 1) POLAR ends faceINSIDE & OUTSIDEcell [where water is] 2) NONPOLAR tails faceeach other inside bilayer [to avoid water]

  3. Outside of cell Carbohydrate chains Proteins Cell membrane Protein channel Inside of cell (cytoplasm) Lipid bilayer

  4. II. FUNCTION: SELECTIVE PERMEABILITY= allows only certain materials to go into & out of cell

  5. a.Why doesn’t the cell membrane let everything through? HOMEOSTASIS! - Cells maintain a stable environment by controlling what enters & leaves.

  6. III. Cellular Transport – Two Major Types (Passive & Active Transport) • Passive Transport= moves molecules across cell mem. using NO ENERGY • Movement going with the concentration gradient(normal flow)

  7. A. Types of Passive Transport • Diffusion – molecules move from HIGH conc. to LOW conc. • a. Small molecules: O2, CO2 • b. Slow process

  8. 2. Facilitated Diffusion – movement of molecules with help of a carrier protein

  9. Moves large molecules • like Glucose and Fructose (C6H12O6) b. Faster than diffusion

  10. http://www.sirinet.net/~jgjohnso/homeostasis.html

  11. 3. Osmosis– diffusion of WATERacross cell membrane * H2O moves to area with LESS WATER

  12. a. Direction of Osmosis: 1) Hypotonic Environment = H2O moves INTO cell & CELLEXPANDS

  13. 2) Hypertonic Environment= H2O moves OUT OF cell & CELLSHRINKS

  14. 3) Isotonic Environment= H2O moves INTO & OUT OF cell & cell staysNORMAL SIZE

  15. * EQUILIBRIUM = concentration of molecules is same everywhere * Molecules never stop moving – even at equilibrium

  16. PROBLEM for Cells?Cell membranes areSELECTIVELY PERMEABLE

  17. 2. 2nd Type of Transport  Active Transport moves molecules across cell membrane using ENERGY

  18. B. Types of Active Transport 1. TransportProteins: in membrane- move substances from low to high concentration. (opposite of how it wants to move)

  19. PUMPS • Sodium-Potassium Pump moves Na+and K +ions • Uses _______________________ called ____________ to move molecules • Example: nerve cellsNa+is pumped out of cells at same time K +is taken into cells • Protein pump moves H+ ions Examples: • Lysosomes need acidic conditions for digestion • Photosynthesis/Respiration (more on this to come in Ch 8 & 9) membrane proteins pumps

  20. Na+and K + PUMP

  21. PROTON PUMP Moves Protons across membrane = ___ ions H+

  22. 2.Endocytosis = cell surrounds & ingests materials fromOUTSIDEtoINSIDE cell using VESICLES

  23. http://www.sirinet.net/~jgjohnso/homeostasis.html

  24. a. Steps: 1) membrane folds in & forms pocket 2) Pocket closes & pinches off in cell vesicle 3) vesicle fuses w/ organelles to release contents

  25. 3. Exocytosis –releases large amounts of material to theOUTSIDE of the cell using VESICLES

  26. a. Steps: • Vesicle forms, travels to & fuses w/ cell mem. • Vesicle opens to outside & releases contents

  27. INSULIN being released by pancreas cells using exocytosis

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