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Download CELL MEMBRANE FUNCTIONS - Hacked By Team System Dz
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CELL MEMBRANE STRUCTURE & FUNCTIONS PASSIVE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION AND ACTIVE TRANSPORT Hydrophilic head WATER Hydrophobic tail WATER Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein TECHNIQUE RESULTS Extracellular layer Knife Plasma membrane Proteins Inside of extracellular layer Cytoplasmic layer Inside of cytoplasmic layer Lateral movement (~107 times per second) Flip-flop (~ once per month) (a) Movement of phospholipids Fluid Unsaturated hydrocarbon tails with kinks Viscous Saturated hydrocarbon tails (b) Membrane fluidity Cholesterol (c) Cholesterol within the animal cell membrane Cell Membrane Structures • Recognition Factors • Antenna that capture required solutes/hormnones • Amphipathic nature of the phospholipids and its consequences • Integral Proteins Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE MEMBRANE PROTEINS Signaling molecule Enzymes ATP (a) Transport Receptor Signal transduction (b) Enzymatic activity (c) Signal transduction (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM) Glycoprotein (d) Cell-cell recognition N-terminus C-terminus Helix EXTRACELLULAR SIDE CYTOPLASMIC SIDE Importance ER 1 1. Acquire molecules & Ions 2.Transport into and out of cell through membrane Transmembrane glycoproteins Secretory protein Glycolipid Golgi 2 apparatus Vesicle 3 4 3.Transport WITHIN the cell Secreted protein Plasma membrane: Cytoplasmic face Extracellular face Transmembrane glycoprotein Membrane glycolipid 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: Cell membrane function, con’t b. impermeable to: - DIFFUSION SIMPLE DIFFUSION REQUIRES A CONCENTRATION GRADIENT FACILITATED DIFFUSION REQUIRES A CONCENTRATION GRADIENT AND A PROTEIN TRANSPORTER Molecules of dye Membrane (cross section) WATER Net diffusion (a) Diffusion of one solute Net diffusion Equilibrium Relate to Lab: Glucose, Starch. NaCl, Proitein Net diffusion Net diffusion (b) Diffusion of two solutes Net diffusion Net diffusion Equilibrium Equilibrium EXTRACELLULAR FLUID Channel protein Solute CYTOPLASM (a) A channel protein Carrier protein (b) A carrier protein Solute ACTIVE TRANSPORT REQUIRES A PROTEIN TRANSPORTER AND ATP ENERGY Active transport: ATP EXTRACELLULAR FLUID Na+ [Na+] high [K+] low Na+ Na+ Na+ Na+ Na+ Na+ Na+ CYTOPLASM 1 Na+ [Na+] low [K+] high P ADP 2 ATP P 3 P P 6 5 4 – ATP EXTRACELLULAR FLUID + – + H+ H+ Proton pump H+ – + H+ H+ – + CYTOPLASM – H+ + – + H+ ATP – H+ + H+ Proton pump H+ – H+ + – H+ + H+ Diffusion of H+ Sucrose-H+ cotransporter H+ Sucrose – – + + Sucrose REVIEW Passive transport Active transport ATP Diffusion Facilitated diffusion Osmosis • Passive Diffusion of Water Dissociation of ions in solution Aquaporins Osmotic concentration Free Energy Water Potential 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: ENVIRONMENT 99% water Hypotonic solution H2O Isotonic solution H2O H2O Hypertonic solution H2O (a) Animal cell Lysed H2O Normal H2O Shriveled H2O H2O (b) Plant cell Turgid (normal) Flaccid Plasmolyzed Cell with less than 1 % Cell with less SOLUTE (freshwater cell than 1 % solute with more than 99% water) Cell Environment with greater than 10% SOLUTE (less than 90 % water) Environment Osmotic or Solute Potential - Free Energy Osmotic Potential Osmotic Pressure Water Potential Ψ “Cell” 0.03 M sucrose 0.02 M glucose Environment: 0.01 M sucrose 0.01 M glucose 0.01 M fructose Lower concentration of solute (sugar) Higher concentration of sugar H2O Selectively permeable membrane Osmosis Same concentration of sugar Additional transport Mechanisms • Bulk Transport • Endocytosis – Phagocytosis – Pinocytosis • Receptor-mediated endocytosis PHAGOCYTOSIS EXTRACELLULAR FLUID 1 µm CYTOPLASM Pseudopodium Pseudopodium of amoeba “Food” or other particle Bacterium Food vacuole Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM) PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit and a coated vesicle formed during receptormediated endocytosis (TEMs) Coat protein Plasma membrane 0.25 µm
