Cells and DiffusionToday’s Learning Objectives: Name the method by which substances move in and out of cells Define diffusion State when diffusion will stop From diagrams, predict the direction of movement of substances by diffusion State which substances enter and leave living cells by diffusion Give one reason why diffusion is important to whole organisms
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Substances have topass into and out of cells These movements most commonly occur by diffusion Diffusion is the movement of molecules from an area of HIGH concentration to an area of LOW concentration until they are EVENLY spread
Food molecules Oxygenmolecules Carbon dioxide molecules Diffusion in or out of a living cell
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Cells and OsmosisToday’s Learning Objectives: Name the method by which water passes in and out of cells Explain what a selectively permeable membrane is State what osmosis is using the terms selectively permeable membrane and concentration gradient Identify water concentration gradients when given solute concentrations Predict the direction of water movement between two solutions of know concentration Describe and predict a visking tubing experiment
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OSMOSIS isthe special diffusion of WATER from a HIGH WATER concentration to a LOW WATER concentration through a SELECTIVELY PERMEABLE MEMBRANE A membrane which is selectively permeable allows certain molecules to pass through but not others.
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Membrane fully permeableto small molecules e.g. water Membrane slowly permeable to larger molecules e.g. sugar Membrane is not permeable to huge molecules e.g. starch Selectively permeable membrane Nucleus Cytoplasm
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Concentration Gradient 99%water 1% sugar 95% water 5% sugar Higher concentration of water Lower concentration of water
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Lower concentration ofwater Higher concentration of water Water moves down a concentration gradient by OSMOSIS from high to low concentration Water molecule Sugar molecule Selectively permeable membrane
Water Concentrations A dilute sugar solution has a high water concentration A concentrated solutions has a low water concentration Water moves in or out of a cell depending on whether the water concentration outside the cell is higher or lower than the water concentration inside the cell
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Water will moveinto the cell Water will move out of the cell Water concentration is equal inside and outside the cell. Solution outside is hypotonic Solution outside is Hypertonic Solution outside is isotonic
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Hypotonic, Hypertonic, IsotonicHypotonic . Has a higher water concentration and a low solute concentration….. Hypertonic Has a lower water concentration and a high solute concentration….. Isotonic Has a water concentration and solute concentration the same…… as the solution in contact
