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CELL MEMBRANE STRUCTURE & FUNCTIONS

CELL MEMBRANE STRUCTURE & FUNCTIONS. PASSIVE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION AND ACTIVE TRANSPORT. WATER. Hydrophilic head. Hydrophobic tail. WATER. Phospholipid bilayer. Hydrophobic regions of protein. Hydrophilic regions of protein. TECHNIQUE. RESULTS. Extracellular

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CELL MEMBRANE STRUCTURE & FUNCTIONS

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  1. CELL MEMBRANE STRUCTURE & FUNCTIONS PASSIVE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION AND ACTIVE TRANSPORT

  2. WATER Hydrophilic head Hydrophobic tail WATER

  3. Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein

  4. TECHNIQUE RESULTS Extracellular layer Proteins Inside of extracellular layer Knife Cytoplasmic layer Plasma membrane Inside of cytoplasmic layer

  5. Lateral movement (~107 times per second) Flip-flop (~ once per month) (a) Movement of phospholipids Fluid Viscous Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails (b) Membrane fluidity Cholesterol (c) Cholesterol within the animal cell membrane

  6. Cell Membrane Structures • Recognition Factors • Antenna that capture required solutes/hormnones • Amphipathic nature of the phospholipids and its consequences • Integral Proteins

  7. Fibers of extracellular matrix (ECM) Carbohydrate Glyco- protein Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE

  8. Signaling molecule Enzymes Receptor MEMBRANE PROTEINS ATP Signal transduction (b) Enzymatic activity (a) Transport (c) Signal transduction Glyco- protein (d) Cell-cell recognition (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM)

  9. EXTRACELLULAR SIDE N-terminus C-terminus CYTOPLASMIC SIDE  Helix

  10. ER 1 Transmembrane glycoproteins Secretory protein Glycolipid Importance1. Acquire molecules & Ions2.Transport into and out of cell through membrane3.Transport WITHIN the cell 2 Golgi apparatus Vesicle 3 Plasma membrane: Cytoplasmic face 4 Extracellular face Transmembrane glycoprotein Secreted protein Membrane glycolipid

  11. Cell Membrane Function Problems and Solutions 1. Relative concentrations a. Passive Transport b. Active Transport 2. Lipid bilayers are impermeable to most essential molecules and ions a. permeable to:

  12. Cell membrane function, con’t b. impermeable to: - - -

  13. DIFFUSION SIMPLE DIFFUSION REQUIRES A CONCENTRATION GRADIENT FACILITATED DIFFUSION REQUIRES A CONCENTRATION GRADIENT AND A PROTEIN TRANSPORTER

  14. Molecules of dye Membrane (cross section) WATER Equilibrium Net diffusion Net diffusion (a) Diffusion of one solute

  15. Relate to Lab: Glucose, Starch. NaCl, Proitein Equilibrium Net diffusion Net diffusion Net diffusion Net diffusion Equilibrium (b) Diffusion of two solutes

  16. EXTRACELLULAR FLUID Channel protein Solute CYTOPLASM (a) A channel protein Solute Carrier protein (b) A carrier protein

  17. ACTIVE TRANSPORT REQUIRES A PROTEIN TRANSPORTER AND ATP ENERGY

  18. Active transport: ATP

  19. EXTRACELLULAR FLUID Na+ [Na+] high Na+ [K+] low Na+ Na+ Na+ Na+ Na+ Na+ ATP [Na+] low P Na+ P [K+] high CYTOPLASM ADP 2 3 1 K+ K+ K+ K+ K+ P K+ P 6 5 4

  20. – EXTRACELLULAR FLUID + – ATP + H+ H+ Proton pump H+ – + H+ H+ H+ – + CYTOPLASM H+ – +

  21. – + H+ ATP H+ – + H+ Proton pump H+ – + H+ H+ – + Diffusion of H+ H+ Sucrose-H+ cotransporter H+ – + Sucrose – + Sucrose

  22. Passive transport Active transport REVIEW ATP Facilitated diffusion Diffusion

  23. Osmosis • Passive Diffusion of Water Dissociation of ions in solution Aquaporins Osmotic concentration Free Energy Water Potential

  24. Tonicity of cell IN COMPARISON TO the environment: The cell is ________in comparison to the environment. Hence, water will move from _____________________ to ____________. The results: Cell Interior: Less than 1% solute ENVIRONMENT 99% water

  25. Hypotonic solution Isotonic solution Hypertonic solution H2O H2O H2O H2O (a) Animal cell Lysed Normal Shriveled H2O H2O H2O H2O (b) Plant cell Turgid (normal) Flaccid Plasmolyzed

  26. Cell with less than 1 % SOLUTE (freshwater cell with more than 99% water) Cell with less than 1 % solute Environment with greater than 10% SOLUTE (less than 90 % water)

  27. Environment: 0.01 M sucrose 0.01 M glucose 0.01 M fructose “Cell” 0.03 M sucrose 0.02 M glucose

  28. Higher concentration of sugar Lower concentration of solute (sugar) Same concentration of sugar H2O Selectively permeable membrane Osmosis

  29. Additional transport Mechanisms • Bulk Transport • Endocytosis • Phagocytosis • Pinocytosis • Receptor-mediated endocytosis

  30. PHAGOCYTOSIS EXTRACELLULAR FLUID CYTOPLASM 1 µm Pseudopodium Pseudopodium of amoeba “Food” or other particle Bacterium Food vacuole Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM)

  31. PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle

  32. RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit and a coated vesicle formed during receptor- mediated endocytosis (TEMs) Coat protein Plasma membrane 0.25 µm

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