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

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Presentation on theme: "CELL MEMBRANE STRUCTURE & FUNCTIONS PASSIVE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION AND ACTIVE TRANSPORT."— Presentation transcript:

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

2 Hydrophilic head WATER Hydrophobic tail WATER

3 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein

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

5 Lateral movement (~10 7 times per second) Flip-flop (~ once per month) (a) Movement of phospholipids (b) Membrane fluidity Fluid Viscous Unsaturated hydrocarbon tails with kinks Saturated hydro- carbon tails (c) Cholesterol within the animal cell membrane Cholesterol

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) Glyco- protein Microfilaments of cytoskeleton Cholesterol Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Carbohydrate

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

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

10 Importance 1. Acquire molecules & Ions 2.Transport into and out of cell through membrane 3.Transport WITHIN the cell ER 1 Transmembrane glycoproteins Secretory protein Glycolipid 2 Golgi apparatus Vesicle 3 4 Secreted protein Transmembrane glycoprotein Plasma membrane: Cytoplasmic face Extracellular face 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, cont b. impermeable to: -

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

14 Molecules of dyeMembrane (cross section) WATER Net diffusion (a) Diffusion of one solute Equilibrium

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

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

17 ACTIVE TRANSPORT REQUIRES A PROTEIN TRANSPORTER AND ATP ENERGY

18 Active transport: ATP

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

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

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

22 REVIEW Passive transport Diffusion Facilitated diffusion Active transport ATP

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

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

25 Hypotonic solution (a ) Animal cell (b ) Plant cell H2OH2O Lysed H2OH2O Turgid (normal) H2OH2O H2OH2O H2OH2O H2OH2O Normal Isotonic solution Flaccid H2OH2O H2OH2O Shriveled Plasmolyzed Hypertonic solution

26 CellEnvironment Osmotic or Solute Potential - Free Energy Osmotic Potential Osmotic Pressure Water Potential Ψ Environment with greater than 10% SOLUTE (less than 90 % water) Cell with less than 1 % solute Cell with less than 1 % SOLUTE (freshwater cell with more than 99% 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 Lower concentration of solute (sugar) H2OH2O Higher concentration of sugar Selectively permeable membrane Same concentration of sugar Osmosis

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

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

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

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


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