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Transcript
MOVEMENT OF SUBSTANCES DIFFUSION 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 Surface area : volume ratio Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________ Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________ Passive Transport • Cell uses no energy • Molecules move randomly • Molecules spread out from an area of high concentration to an area of low concentration. 3 Types of Passive Transport 1. Diffusion 2. Facilitative Diffusion – diffusion with the help of transport proteins 3. Osmosis – diffusion of water Diffusion Before Region of high concentration After Diffusion of Liquids Diffusion in Life Diffusion of Bromine Diffusion of Bromine Diffusion in Living Organisms • 2nd Law of Thermodynamics governs biological systems – universe tends towards disorder (entropy) Diffusion movement from high low concentration Diffusion in Living Organisms Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY Cell Membrane 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 Phospholipid Lipid Bilayer Fluid Mosaic Polar heads love water & Model of the cell dissolve. membrane Non-polar tails hide from water. Carbohydrate cell markers Proteins Structure of the Cell Membrane Outside of cell Proteins Lipid Bilayer Transport Protein Phospholipids Inside of cell (cytoplasm) Go to Section: Carbohydrate chains Cell Membrane is Selectively Permeable Diffusion Through Phospholipid Bilayer • What molecules can get through directly? – fats & other lipids What molecules can NOT get through directly? lipid inside cell H2O salt NH3 polar molecules ions salts, ammonia large molecules starches, proteins outside cell sugar aa H2O Passive Transport: Facilitated Diffusion Glucose molecules Cellular Transport From aHigh Concentration High Cell Membrane Low Concentration Through a Transport Protein Low Protein channel Passive Transport: Facilitated Diffusion 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 A B Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein 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 Summary No energy needed Passive transport Diffusion is a passive transport Diffusion in living organism Molecules move from area of high to low concentration Across cell membrane