Membrane_structure_and_function

Membrane_structure_and_function - Membranes-The fluid...

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Unformatted text preview: Membranes-The fluid mosaic model Membranes-The Evidence for the drifting of membrane proteins Evidence QuickTime ™ and a Sorenson Video 3 decompressor are needed to see this picture. The synthesis and structure of a fat, or triacylglyceride The Figure 5.12 Examples of saturated and unsaturated fats and fatty acids Figure 10-3 Molecular Biology of the Cell (© Garland Science 2008) Figure 5.14 Two structures formed by self-assembly of phospholipids in aqueous environments Figure 10-7 Molecular Biology of the Cell (© Garland Science 2008) Figure 10-8 Molecular Biology of the Cell (© Garland Science 2008) Effects of unsaturation of phospholipids Effects Fluidity of membrane Important in cold blooded animals Saturated fats have higher melting point Conversion to cholesterol Harder to convert if more double bonds are present Figure 7.10 Figure glycolipid Cholesterol Cholesterol Cholesterol Cholesterol is also found in the membrane of cells membrane Regulates fluidity of Regulates cell membranes The more cholesterol The the less fluid the membrane. membrane. Some functions of membrane proteins Some Transport Transport Permeability of membranes Permeability Can Can pass through the lipid bilayerlipid Small Small polar molecules (water) (water) Non-polar molecules Small Small molecules and those less strongly associated with water will pass across membrane membrane Cannot Cannot pass through the lipid bilayerthe Large polar molecules Charged molecules The structure of a transmembrane protein The Porin Porin http://www.ncbi.nlm.nih.gov/Structure/mmdb/mmdbsrv.cgi?uid=66323 Passive and active transport compared Passive Figure 7.11 The diffusion of solutes across membranes Figure The contractile vacuole of Paramecium: an evolutionary adaptation for osmoregulation Paramecium Figure 7.15 Two models for facilitated diffusion Figure Diffusion down concentration gradient The sodium-potassium pump: a specific case of active transport The Figure 7.19 Co-transport Figure Figure 7.18 An electrogenic pump Figure Electrogenic transport: This is an active transport process driven by electric potentials. Passive transport Passive Diffusion Free-down concentration gradient Across membrane With or without channel proteins Facilitated diffusion Active transport Active Pumps Pumps molecules or ions against a concentration gradient concentration Requires the input of energy Requires (e.g. ATP, light) Sodium (Na+) Potassium (K+) pump Sodium Cells maintain low intracellular [Na+] 440mM Cells maintain high intracellular [K+] 560mM Ions Ions outside, 50 mM inside inside, 90mM outside cannot diffuse through lipid bilayer Sodium-Potassium dependent ATPase Attachment to cytoskeleton Attachment Intercellular joining Intercellular Intercellular junctions in animal and plant tissues Intercellular Signal transduction Signal The three types of endocytosis in animal cells cells http://highered.mcgrawhill.com/sites/00724373 16/student_view0/chapt er6/animations.html Exocytosis Exocytosis ...
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