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MOVEMENT OF SUBSTANCES DIFFUSION
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Learning Outcomes After completing this chapter, you will able to : Define diffusion as the movement of molecules from a region of their higher concentration to a region of their lower concentration down a concentration gradient
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Surface area : volume ratio Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________ Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________
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Passive Transport Cell uses no energy Molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration.
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3 Types of Passive Transport 1.Diffusion 2.Facilitative Diffusion – diffusion with the help of transport proteins 3.Osmosis – diffusion of water
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Diffusion Before After Region of high concentration
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Diffusion of Liquids
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Diffusion in Life
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Diffusion of Bromine
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Diffusion in Living Organisms 2nd Law of Thermodynamics governs biological systems – universe tends towards disorder (entropy) Diffusion movement from high low concentration Diffusion movement from high low concentration
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Diffusion in Living Organisms PASSIVE Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY
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Structure of cell membrane Lipid Bilayer -2 layers of phospholipids a.Phosphate head is polar (water loving) b.Fatty acid tails non-polar (water fearing) c.Proteins embedded in membrane Cell Membrane Phospholipid Lipid Bilayer
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Proteins Polar heads love water & dissolve. Non-polar tails hide from water. Carbohydrate cell markers Fluid Mosaic Model of the cell membrane
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Outside of cell Inside of cell (cytoplasm) Lipid Bilayer Proteins Transport Protein Phospholipids Carbohydrate chains Structure of the Cell Membrane Go to Section:
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Cell Membrane is Selectively Permeable
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Diffusion Through Phospholipid Bilayer What molecules can get through directly? – fats & other lipids inside cell outside cell lipid salt aa H2OH2O sugar NH 3 What molecules can NOT get through directly? polar molecules H2OH2O ions salts, ammonia large molecules starches, proteins
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High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel Passive Transport: Facilitated Diffusion Transport Protein Through a Cellular Transport From a- High Low
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Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane a.Transport Proteins are specific – they “select” only certain molecules to cross the membrane b.Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Passive Transport: Facilitated Diffusion Carrier Protein AB
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Diffusion in Living Organisms Diffusion of digested food through the cell lining the small intestine and into the blood Diffusion of oxygen into a root hair cell
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Summary Passive transport No energy needed Molecules move from area of high to low concentration Diffusion is a passive transport Diffusion in living organism Across cell membrane
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