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Exam 2 notes! - Cell is the minimum organization of living...

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Cell is the minimum organization of living matter CELL MEMBRANE MODELS (plasma membrane): - All cells have a thin outer covering - Plasma membrane or cell membrane - Early models inferred the structure from chemical and permeability properties of the membrane - Cell membrane made up of phospholipids - Permeable to ions, water Fluid-Mosaic Model 2 layers of phospholipids as before, but now exposed proteins in a mosaic patterns, not a continuous layer pores bounded by protein as before fluidity: proteins and phospholipids can move (dynamic structure), evidence from hybrid cells - Phospholipid bilayer with a mosaic of associated proteins - Figure 7.7 Cell Coats: (not a separate entity from the cell membrane) glycocalyx composed of glycolipids, glycoproteins (short chain carbohydrates attached) - molecules that are part of the cell membrane - important feature for cell/cell recognition - Function: cell recognition Why do membranes exist ??? A) structural: need to keep contents of the cytoplasm inside of something; holds the cell together B) Functional properties: - Maintain concentrations of molecules and ions - Create free energy gradients - Orient molecules into functional complexes Biological Systems: (with membranes)
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Osmosis: net movement of water across (through) a semi-permeable membrane (ie permeable to water, but not to solutes) Relative Relationship: Which side does the water have the greatest free energy or is most concentrated? 1M sucrose OR Distilled water Distilled water In which direction will there be a net movement of water? Sodium chloride does dissociate in water, 1M Na+ & 1M Cl- (2 moles); NaCl has more material in solution, increasing the entropy of the water molecules making the water move from L to R 1M sucrose 1M NaCl Water permeable membrane In which direction will there be a net movement of water? To the RIGHT Equilibrium point would be 1.5 M on each side glucose 1M Sucrose 2M Sucrose 2M Glucose (1.5) 1M Glucose (1.5) 2.5 M 3.5 M After water movement the glucose goes to equilibrium point** Membrane permeable to H 2 0 and Glucose Terminology of Solutions Relative to one another: Hyperosmotic/ hypertonic: more concentrated Isosmotic/ isotonic: Equal Concentrated Hypoosmotic/ hypotonic: less concentrated Clicker ?: A single celled freshwater organism, such as a Paramecium, is transferred to saltwater. Which of the following would happen The cell will shrink Clicker ? Water will ___ the cells of a fish living in fresh water because of the process of osmosis. MOVE INTO Factors involved in the permeability * size and shape of molecules
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- Really small molecules (like oxygen) will pass right through the membrance * solubility in lipids - Lipids are soluble in other lipids, non-polar things pass right through the membrane * net electric charge - typically not permeable through the cell membrane * chemical properties ------But water moves freely across the membrane------ * important to study the movement of water ** water is the universal solvent in biological systems
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This note was uploaded on 12/07/2010 for the course BIOL 1201 taught by Professor Wishtichusen during the Fall '07 term at LSU.

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Exam 2 notes! - Cell is the minimum organization of living...

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