Cell membrane 9-13 - Cell is the minimum organization of...

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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?
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