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SUNLIGHT ENERGY Cell Structure Thursday, January 22, 2009 9:27 AM 1. Prokaryotic Cells o Archaea (ancient, live in extreme conditions) and Bacteria (common bacteria) o DNA is not in a nucleus o No membrane-bound organelles o Most prokaryotic cells have a cell wall outside the plasma membrane and many have a thick jellylike capsule around the wall. Soap causes the bacteria to release from hands when washing them 2. Eukaryotic Cells o Have nucleus and membrane bound organelles o Plant Cells- Large central vacuole, cell wall, chloroplast o Animal Cells - membrane rounded and deformable, centrioles o Plasma Membrane Defines the cell as a distinct entity Made up of double layer of lipids Membrane has fluid components, is a fluid substance. o Membrane: Danielli's unit membrane hypothesis (1940) Lipid Layer Lipids and lipid soluble substances move through membrane with ease Pores=Sieve Theory Cells can't keep water in or out, so must have holes in membrane Various ions pass with differential ease: Charge Different properties include wettability (Hydrophilic) = Protein layer Unit in a membrane is protein lipid protein "Pumpernickel cream cheese Pumpernickel" Fluid Mosaic Model The lipids are a matrix in which the proteins float. Because they are floating they are mosaic. Fluid properties Different kinds of lipids in membrane. Different ones give them different structure Membrane: mosaic of lipids and proteins Most phospholipids and some proteins can drift through membrane 3. Why are Cells so Small? o S to V ratio o Bigger cell: less surface area per unit volume S/V
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o Above a certain size, material cannot be moved in or out fast enough Ball of certain shape. If doubled volume of ball wouldn’t double surface area Whenever in a cell or organism, wrinkled or folding membrane helps function better 4. Inside of a Cell o Nucleus The nucleus keeps eukarotic DNA molecules organized and separated from the metabolic machinery of the cytoplasm
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This note was uploaded on 11/05/2011 for the course BIOL 101 taught by Professor Hogan during the Fall '08 term at UNC.

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