Plasma Membrane

1. Plasma Membrane Structure and Function

2. Fluid Mosaic Modelof Membrane Structure Oligosaccharides PhospholipidBilayer Membrane Proteins OuterSurface Cholesterol Cytoplasm

3. Macromolecules found in Membranes • Lipids • Phospholipid bilayer • Cholesterol • Proteins • Transport proteins • Receptor proteins • Recognition proteins • Carbohydrates • Oligosaccharides on glycoproteins

4. Polar group Glycerol Fatty Acid Fatty Acid Fatty Acid Fatty Acid Fatty Acid Phospholipid Structure Change from Triglyceride to Phospholipid Glycerol

5. The plasma membrane “fluid” is a double layer of phospholipids.

6. The plasma membrane “mosaic” is a collection of proteins.

7. Functions of Membrane Macromolecules • Lipids • Phospholipid bilayer • Forms boundary to isolate cell contents from environment • Restricts passage of hydrophilic substances across the membrane • Cholesterol • Increases bilayer strength, flexibility • Reduces membrane fluidity • Reduces permeability to water-soluble substances

8. Functions of Membrane Macromolecules • Proteins • Transport proteins • Regulate movement of water soluble substances • Channel proteins have pores that allow passage of ions and small water-soluble molecules • Carrier proteins bind to molecules and change shape for delivery across membrane

9. Functions of Membrane Macromolecules • Proteins • Receptor proteins • Docking site for molecules outside the cell • Trigger internal cellular response • Recognition proteins • Identification tags • Oligosaccharides aid in cell-cell recognition • Cell-surface attachment sites

10. Which component would have an oligosaccharide attached? Which component regulates membrane fluidity? Which component assists in movement of water-soluble substances across the membrane? Cholesterol Receptor Protein Phospholipid Bilayer Transport Protein Recognition Protein Applying Your Knowledge

11. Movement of substances across the cell membrane Passive transport Substances move from [high][low] No energy input required Simple Diffusion, Facilitated Diffusion, Osmosis Active transport Substances move from [low][high] Requires energy input Protein carriers, Endocytosis, Exocytosis Transport Processes

12. Diffusion of Dye in Water RandomDispersal Dispersing Time 0 Time 1 Time 2 SteepConcentrationGradient ReducedConcentrationGradient NoConcentrationGradient

13. Simple Diffusion (extracellular fluid) Now known to require transport proteins called aquaporins Some moleculesdiffuse freelyacross (cytoplasm) (lipid soluble molecules, CO2, O2, H2O )

14. Facilitated Diffusion: Use of Carriers to Assist with Diffusion DiffusionChannelProtein (OutsideCell) Molecule inTransit DiffusionGradient Carrier proteinhas binding sitefor molecule Carrier protein changesshape, transportingmolecule across membrane Molecule entersbinding site Carrier protein resumesoriginal shape (Inside Cell)

15. Diffusion of water across a differentially permeable membrane Water moves from [high]  [low] Osmosis

16. “Free” watermolecule: can fitthrough pore “Bound” water moleculesclustered around sugar:cannot fit through pore

17. Shriveled RBCs Normal RBCs Swollen RBCs The Effects of Osmosis Hypertonic Solution Isotonic Solution Hypotonic Solution Equal movement of waterinto and out of cells Net movement ofwater out of cells Net movement ofwater into cells

18. Active Transport with Protein Carrier TransportedMolecule Outside Cell 1 2 3 4 Inside Cell EnergyProvider Spent EnergyProvider

19. Endocytosis Pinocytosis Receptor-mediatedEndocytosis (extracellular fluid) nutrients receptors 1 1 (extracellular fluid) 3 2 vesicle containingextracellularfluid) 2 coatedpit forming (cytoplasm) 3 coatedvesicle 4 (cytoplasm) cell food particle particle enclosedin food vacuole pseudopod Phagocytosis

20. Endocytosis • Active process for movement of large molecules and organisms • Substance is taken in by vesicle formed from cell membrane • Phagocytosis: solid substance in vesicle • Pinocytosis: liquid droplets in vesicle • Receptor-Mediated Endocytosis: incoming substance binds to receptor

21. 0.1 Micrometer Receptor-mediated Endocytosis I extracellular particlesbound to receptors (extracellular fluid) a b plasma membrane proteincoating (cytoplasm) coatedpit Begins with a shallowpit in plasma membrane Pit deepens Pit is coated withprotein

22. coatedvesicle d 0.1 Micrometer Receptor-mediated Endocytosis II c Pit deepens further andbegins to pinch off Eventually becomes acoated vesicle

23. Exocytosis • Substance is expelled after being enclosed in a vesicle within the cell • Used to move large molecules out of the cell

24. SecretedMaterial (extracellular fluid) plasma membrane 3 2 Vesicle Exocytosis 1 (cytoplasm)

25. Which methods allow movement into the cell? Which methods involve movement of liquid? Which methods involve movement from [low]  [high]? Facilitated Diffusion Endocytosis Osmosis Exocytosis Active Transport Applying Your Knowledge 6. Simple Diffusion 7. Pinocytosis 8. Receptor-mediated endocytosis 9. Phagocytosis 1, 2, 3, 5, 6, 7, 8, 9 2, 3, 6, 7 2, 4, 5, 7, 8, 9

26. Plasma membrane(edge view) Tight junctionsseal membranesof adjacent cellstogether Cells liningbladder Tight junctionsformed by strandsof protein Tight Junction Cell Attachment Structures Small intestine Plasma membrane(edge view) Protein filamentsin cytoplasm Cells liningsmall intestine Protein strandsholding cellstogether desmosome Desmosome

27. Plasma membrane(edge view) Cell wall(edge view) Root Middle lamella(edge view) Root cells Plasmodesmataconnect insidesof adjacent cells Plasmodesmata Cell Communication Structures Animals Plants Liver Plasma membrane(edge view) Liver cells Gap Junctions:pairs of channelsconnect insides ofadjacent cells desmosome Gap Junctions