Presentation on theme: "Topic 2 Diffusion and Osmosis"— Presentation transcript:
1 Topic 2 Diffusion and Osmosis Unit 1 CellsTopic 2Diffusion and Osmosis
2 Diffusion and Osmosis Learning objectives: By the end of the lesson you should be able to:Describe diffusion as movement of substances like sugar and oxygen in and out of cells.Explain the importance of diffusion to cells.
3 Concentration Gradient Diffusion is the movement of a substance from __________________________________________ __________________________________________A region of high concentration to a region of where it is at aLower concentration until the concentration is equalConcentration GradientThe difference between a high and a low concentration is called a ____________________Substances __Concentration gradientDiffuse down a concentration gradientDiffusion and CellsMany substances ______________________________ important in living processes of a cell, enter and leave the cell by________________.These small molecules are able to ______________________(carbon dioxide, oxygen, dissolved food and waste),diffusionMove through the cell membrane
6 Importance of Diffusion Diffusion is the means by which ________________ in living organisms e.g. humansGases are exchangedLungsOxygenBlood with _________ and ______________________concentrationBlood with ___________ and ____________ concentrationHigh oxygenLow oxygenCarbon dioxideLow carbonHigh CarbonDioxideDioxideCarbon dioxideOxygenBody Tissues
7 Efficiency of surfaces where diffusion takes place Where diffusion takes place in organisms the efficiency of the process can be increased by one or more of the following.___________ allowing _____________ with the diffusing substances.Large surface areaMaximum contact_______________ often only one cell thick ________________________________________________________ that have diffused and so to maintain the concentration gradient._____________, substances need to be ___________________Thin surfaceAllowing speedy diffusionGood blood supply to carry away substancesMoist surfaceDissolved in order to diffuse
8 Solutions A solution is made from ____________________________ e.g. water_________________________________ e.g. salt, glucoseLiquid known as the solventDissolved substances known as the soluteDescribing solutionsSolutions can be described in a number of ways, these includePercentageThe solute % plus the solvent % must add up to ______ e.g. a 10% glucose solution is made from 10% glucose and 90% water.E.g. a 5% salt solution is made up of 5% salt and 95% water100%
9 Molarity Solutions can also be described in terms of their molarity e.g. 1 Molar glucose solution (1M)The higher the number the more solute is in the solutione.g. a 2 M solution contains more solute than a 1M solution
10 Diffusion and Osmosis Learning objectives: By the end of the lesson you should be able to:Explain the movement of water in plant and animal cells by the process of osmosis.Describe the effect of osmosis on plant and animal cells.
11 OsmosisOsmosis is the diffusion of WATER from a HIGH concentration to a LOW concentration across a SELECTIVELY PERMEABLE MEMBRANEMembranesMembranes in cells are_____________________________________ e.g oxygen______________________________________e.g. sugar______________________________________ e.g. starchFreely permeable to very small moleculesSlowly permeable to slightly larger moleculesImpermeable to very large molecules
12 Mechanism of OsmosisOsmosis is the diffusion of water through a selectively permeable membrane.Water _______________________________________ ____________________________________________Will move from where the water concentration is higherTo where the water concentration is lower
13 Selectively Permeable Membrane 5% Sucrose Solution10% Sucrose SolutionSucrose moleculeWater moleculeHigher WaterConcentrationLower water concentrationWater will move in both directions but there will be more movement in this direction.
14 Diffusion and Osmosis Learning objectives: By the end of the lesson you should be able to:Describe the effect of placing cells in a HYPERTONIC solution.Describe the effect of placing cells in an ISOTONIC solution.Describe the effect of placing cells in a HYPOTONIC solution.
15 Comparing Solutions Solutions can be compared in _____________________ Terms of their concentrationSolutions can be compared in ________________________________ solutions have the __________ concentrations of waterIsotonicsameMore water_____________ solution contains _____________ than the solution which it is compared.E.g. a 10% glucose solution is said to be _________ when compared to a 20% glucose solution as it contains ____________ than the 20% solutionA hypotonichypotonicMore water
16 ______________ solution contains ______ water than the solution with which it is compared. A hypertoniclessE.g. a 10% glucose solution is said to be ________ when compared to a 5% glucose solution as it contains _________ than the 5% solutionhypertonicLess waterDistilled water______________________ is completely pure and so is ____________________________________________100% water, it is hypotonic to all other solutions
17 Osmosis and animal cells When _____________________________________ then osmosis will take placeE.g. osmosis in red blood cellsCells are placed in solutions of different concentrationsAppearance of red blood cellSurrounding solutionExplanationIsotonicWater enters and leaves the cell at the same ratehypotonicWater flows into the cellCell swells and burstsThis is called haemolysishypertonicWater flows out of the cellCell shrinksNo net movement of waterNo change in appearance
19 Osmosis in Plant Cells Appearance of plant cells Surrounding Solution ExplanationIsotonicWater enters and leaves the cell at the same rateNo net movement of waterNo change in appearanceHypotonicWater flows into the cell and vacuole swellsCell wall prevents burstingCell is turgidHypertonicWater flows out of the cell and vacuole shrinksMembrane peels away from wall.Cell is plasmolysed
20 Osmosis and Tissues Pieces of tissue e. g Osmosis and Tissues Pieces of tissue e.g. potato cylinders can be placed in different solutionsAppearance of potato cylinderSurrounding solutionDescriptionIsotonic____________________________of cylinderHypotonic_______________ than cylinder in isotonic solutionTurgidHypertonic___________________Than cylinder in isotonic solutionFeels rubbery________Normal length, diameterAnd weightLonger, wider and heavierShorter, thinner and lighterFlaccid
21 Movement of water by Osmosis Where two cells are touching and _____________ ________________________________________ ____________The solutions insidehave different concentrations water will move from one cell to anotherCell ACell B5% solution6% solution94% water95% water______________________ cell __ to cell ____Water will move fromAB