Ap Bio Ch 5 Power Point


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Cel Membrane Structure and Function

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  • Ap Bio Ch 5 Power Point

    1. 1. Cell Membranes
    2. 2. Cell Membrane <ul><li>Functions </li></ul><ul><li>Selectively choose what’s inside or outside the cell…creating a concentration gradient </li></ul><ul><li>Regulate the exchange of substances </li></ul><ul><li>Communicate with other cells </li></ul><ul><li>Attach to other cells </li></ul><ul><li>Regulate biochemical reactions </li></ul>
    3. 3. Phospholipid Review Glycerol Change from Triglyceride to Phospholipid Fatty Acid Fatty Acid Glycerol Polar group Fatty Acid Fatty Acid Fatty Acid
    4. 4. Fluid Mosaic Model of Membrane Structure Oligosaccharides Cytoplasm Membrane Proteins Cholesterol Outer Surface
    5. 5. Membrane Proteins Form a Mosaic <ul><li>Proteins are embedded in the phospholipid bilayer </li></ul><ul><ul><li>Some proteins can float and drift </li></ul></ul><ul><ul><li>Other proteins are anchored by protein filaments in the cytoplasm </li></ul></ul><ul><ul><li>Many proteins have attached carbohydrates ( glycoproteins ) </li></ul></ul>
    6. 7. Membrane Proteins Form a Mosaic <ul><li>Categories of membrane proteins </li></ul><ul><ul><li>Receptor Proteins </li></ul></ul><ul><ul><li>Recognition Proteins </li></ul></ul><ul><ul><li>Enzymatic Proteins </li></ul></ul><ul><ul><li>Attachment Proteins </li></ul></ul><ul><ul><li>Transport Proteins </li></ul></ul>
    7. 8. Membrane Proteins Form a Mosaic <ul><li>Receptor Proteins </li></ul><ul><ul><li>Trigger cellular responses upon binding specific molecules, e.g. hormones </li></ul></ul><ul><li>Recognition Proteins </li></ul><ul><ul><li>Serve as identification tags on the surface of a cell </li></ul></ul>
    8. 10. Membrane Proteins Form a Mosaic <ul><li>Enzymes </li></ul><ul><ul><li>Promote chemical reactions that synthesize or break apart biological molecules </li></ul></ul><ul><li>Attachment Proteins </li></ul><ul><ul><li>Anchor the cell membrane to inner cytoskeleton, to proteins outside the cell, and to other cells </li></ul></ul>
    9. 11. Membrane Proteins Form a Mosaic <ul><li>Transport Proteins </li></ul><ul><ul><li>Include channel and carrier proteins </li></ul></ul><ul><ul><li>Regulate import/export of hydrophilic molecules </li></ul></ul>
    10. 12. Transport Processes <ul><li>How stuff gets across cell membrane. </li></ul><ul><li>Passive transport </li></ul><ul><ul><li>Follows concentration gradient </li></ul></ul><ul><ul><li>Does not require energy </li></ul></ul><ul><li>Facilitated transport </li></ul><ul><ul><li>Follows concentration gradient </li></ul></ul><ul><ul><li>Requires gateway protein </li></ul></ul>
    11. 13. Diffusion <ul><li>All molecules constantly vibrating </li></ul><ul><li>Those in gas and liquid move randomly </li></ul><ul><li>Mixtures tend to become uniform </li></ul><ul><ul><li>Move from high concentration to low </li></ul></ul><ul><ul><li>Concentration gradient </li></ul></ul><ul><ul><li>Doesn’t require energy </li></ul></ul>
    12. 14. Diffusion of Dye in Water Time 0 Steep Concentration Gradient Time 1 Reduced Concentration Gradient Dispersing Time 2 No Concentration Gradient Random Dispersal
    13. 15. Simple Diffusion (extracellular fluid) (cytoplasm) Some molecules diffuse freely across
    14. 16. Facilitated Diffusion: Carriers Carrier protein has binding site for molecule Molecule enters binding site Carrier protein changes shape, transporting molecule across membrane Carrier protein resumes original shape (Inside Cell) (Outside Cell) Diffusion Channel Protein Diffusion Gradient Molecule in Transit
    15. 17. Osmosis <ul><li>Diffusion of water across membrane </li></ul><ul><li>Special case of diffusion </li></ul><ul><ul><li>Ex: Pure water on one side; sugar solution on other </li></ul></ul><ul><ul><li>Sugar molecules can’t cross, but crowd pores </li></ul></ul><ul><ul><li>Water crosses faster toward sugar </li></ul></ul><ul><li>Net water movement toward sugar </li></ul><ul><li>Water follows concentration gradient </li></ul>
    16. 18. Osmotic Factors <ul><li>Compare cell’s environment with cell. </li></ul><ul><li>If environment is: </li></ul><ul><ul><li>Hypotonic : </li></ul></ul><ul><ul><ul><li>“ Hypo-” means environment “<” cell </li></ul></ul></ul><ul><ul><ul><li>Cell gains water </li></ul></ul></ul><ul><ul><li>Hypertonic : </li></ul></ul><ul><ul><ul><li>“ Hyper-” means environment “>” cell </li></ul></ul></ul><ul><ul><ul><li>Cell loses water </li></ul></ul></ul><ul><ul><li>Isotonic : </li></ul></ul><ul><ul><ul><li>“ Iso-” means environment “=” cell </li></ul></ul></ul><ul><ul><ul><li>No change in cell volume </li></ul></ul></ul>
    17. 19. Osmosis I “ Bound” water molecules clustered around sugar: cannot fit through pore “ Free” water molecule: can fit through pore
    18. 20. The Effects of Osmosis Isotonic Solution Equal movement of water into and out of cells Net movement of water out of cells Net movement of water into cells Hypertonic Solution Hypotonic Solution Normal RBCs Shriveled RBCs Swollen RBCs
    19. 21. Active Transport <ul><li>Requires energy </li></ul><ul><li>Ex: Sodium/Potassium pump </li></ul><ul><li>Energy from ATP </li></ul><ul><li>One phosphate per “fare” </li></ul><ul><li>Pumped by flip/flop changes in a membrane protein </li></ul>
    20. 22. Active Transport Steps Inside Cell Outside Cell Energy Provider Spent Energy Provider Transported Molecule 1 2 3 4
    21. 23. Endo- & Exocytosis <ul><li>This is like cell eating & pooping. </li></ul><ul><li>Active processes for large groups of molecules. </li></ul><ul><ul><li>Endocytosis - Engulfment </li></ul></ul><ul><ul><li>Exocytosis - Expulsion </li></ul></ul>
    22. 24. Endocytosis (extracellular fluid) Pinocytosis vesicle containing extracellular fluid) (cytoplasm) 1 2 3 cell (extracellular fluid) (cytoplasm) 1 2 3 4 coated pit forming Receptor-mediated Endocytosis Phagocytosis coated vesicle nutrients receptors food particle pseudopod particle enclosed in food vacuole
    23. 25. Receptor- mediated Endocytosis I Begins with a shallow pit in plasma membrane Pit is coated with protein (cytoplasm) (extracellular fluid) coated pit protein coating extracellular particles bound to receptors plasma membrane Pit deepens a b 0.1 Micrometer
    24. 26. Receptor- mediated Endocytosis II Pit deepens further and begins to pinch off Eventually becomes a coated vesicle c d 0.1 Micrometer coated vesicle
    25. 27. Exocytosis (cytoplasm) 1 Vesicle (extracellular fluid) plasma membrane 2 Secreted Material 3
    26. 28. Attributes of Cells <ul><li>Cell size </li></ul><ul><ul><li>1–100 µm </li></ul></ul><ul><ul><li>Why is there a limit to cell size? </li></ul></ul><ul><ul><ul><li>Surface-to-volume (S/V) ratio </li></ul></ul></ul><ul><ul><ul><li>Distance from surface to center </li></ul></ul></ul>
    27. 29. Surface to Volume Ratio 3 1 3 S/V Ratio 113.1 113.1 4.2 Volume 4/3  r 3 339.4 113.1 12.6 Surface 4  r 2 1.0 3.0 1.0 Radius Grow Break apart
    28. 30. Cell Communication Structures Desmosome desmosome Protein strands holding cells together Protein filaments in cytoplasm Small intestine Plasma membrane (edge view) Cells lining small intestine Tight Junction Tight junctions formed by strands of protein Plasma membrane (edge view) Cells lining bladder Tight junctions seal membranes of adjacent cells together
    29. 31. Cell Attachment Structures Gap Junctions desmosome Gap Junctions: pairs of channels connect insides of adjacent cells Liver Plasma membrane (edge view) Liver cells Plasmodesmata Plasmodesmata connect insides of adjacent cells Plasma membrane (edge view) Root cells Cell wall (edge view) Middle lamella (edge view) Root
    30. 32. The End