311C_F10_Chapter 7

311C_F10_Chapter 7 - Membrane structure function&...

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Unformatted text preview: Membrane structure, function & electrical membrane potentials Chapter 7 Chapter 48 (pages 1050 – 1052) http://science.nhmccd.edu/biol/bio1int.htm#transport • Phospholipids - the most abundant lipid in the plasma membrane • The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it Fig. 7-2 Hydrophilic head WATER Hydrophobic tail WATER Fig. 7-3 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein Membrane lipids • Phospholipids • Sphingolipids • Cholesterol Fig. 7-5a (a) Movement of phospholipids Lateral movement ( ∼ 10 7 times per second) Flip-flop ( ∼ once per month) Membrane fluidity • Each phospholipid has a specific phase transition temperature – Above this temperature, lipid is in liquid crystalline phase & is fluid. – Below this temperature, lipid is in a gel phase and is rigid • Membrane lipids are normally in liquid crystalline phase • As temperatures cool, membranes switch from a fluid state to a solid state • The temperature at which a membrane solidifies depends on the types of lipids • Membranes rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids • Membranes must be fluid to work properly; they are usually about as fluid as salad oil Fig. 7-5b (b) Membrane fluidity Fluid Unsaturated hydrocarbon tails with kinks Viscous Saturated hydro- carbon tails Fig. 7-5c Cholesterol (c) Cholesterol within the animal cell membrane • Cholesterol has different effects on membrane fluidity at different temperatures • At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids • At cool temperatures, it maintains fluidity by preventing tight packing Figure 7.7 Glycoprotein Carbohydrate Microfilaments of cytoskeleton Cholesterol Peripheral protein Integral protein CYTOPLASMIC SIDE OF MEMBRANE EXTRACELLULAR SIDE OF MEMBRANE Glycolipid Membrane Proteins and Their Functions Fibers of extracellular matrix (ECM) http://www.dac.neu.edu/biology/bio1100/movies/fluid_mosaic.mov EXTRACELLULAR SIDE Figure 7.8 N-terminus C-terminus α Helix CYTOPLASMIC SIDE a) Integral membrane proteins – eg. transmembrane proteins b) Peripheral proteins Fig. 7-9 (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) Selective permeability...
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This note was uploaded on 12/04/2010 for the course BIO 311 C taught by Professor Mcclelland during the Fall '09 term at University of Texas.

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311C_F10_Chapter 7 - Membrane structure function&...

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