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Topic 2 Diffusion and Osmosis
Unit 1 Cells Topic 2 Diffusion and Osmosis
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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.
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Concentration Gradient
Diffusion is the movement of a substance from __________________________________________ __________________________________________ A region of high concentration to a region of where it is at a Lower concentration until the concentration is equal Concentration Gradient The difference between a high and a low concentration is called a ____________________ Substances __ Concentration gradient Diffuse down a concentration gradient Diffusion and Cells Many 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), diffusion Move through the cell membrane
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Plant Cell Animal Cell Carbon dioxide Waste Oxygen Dissolved food
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Plant Cell Animal Cell
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Importance of Diffusion
Diffusion is the means by which ________________ in living organisms e.g. humans Gases are exchanged Lungs Oxygen Blood with _________ and ___________ ___________ concentration Blood with ___________ and ____________ concentration High oxygen Low oxygen Carbon dioxide Low carbon High Carbon Dioxide Dioxide Carbon dioxide Oxygen Body Tissues
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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 area Maximum contact _______________ often only one cell thick ___________________________ _____________________________ that have diffused and so to maintain the concentration gradient. _____________, substances need to be ___________________ Thin surface Allowing speedy diffusion Good blood supply to carry away substances Moist surface Dissolved in order to diffuse
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Solutions A solution is made from
____________________________ e.g. water _________________________________ e.g. salt, glucose Liquid known as the solvent Dissolved substances known as the solute Describing solutions Solutions can be described in a number of ways, these include Percentage The 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% water 100%
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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 solution e.g. a 2 M solution contains more solute than a 1M solution
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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.
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Osmosis Osmosis is the diffusion of WATER from a HIGH concentration to a LOW concentration across a SELECTIVELY PERMEABLE MEMBRANE Membranes Membranes in cells are _____________________________________ e.g oxygen ______________________________________e.g. sugar ______________________________________ e.g. starch Freely permeable to very small molecules Slowly permeable to slightly larger molecules Impermeable to very large molecules
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Mechanism of Osmosis Osmosis is the diffusion of water through a selectively permeable membrane. Water _______________________________________ ____________________________________________ Will move from where the water concentration is higher To where the water concentration is lower
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Selectively Permeable Membrane
5% Sucrose Solution 10% Sucrose Solution Sucrose molecule Water molecule Higher Water Concentration Lower water concentration Water will move in both directions but there will be more movement in this direction.
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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.
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Comparing Solutions Solutions can be compared in _____________________
Terms of their concentration Solutions can be compared in _____________________ ___________ solutions have the __________ concentrations of water Isotonic same More 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% solution A hypotonic hypotonic More water
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______________ solution contains ______ water than the solution with which it is compared.
A hypertonic less E.g. a 10% glucose solution is said to be ________ when compared to a 5% glucose solution as it contains _________ than the 5% solution hypertonic Less water Distilled water ______________________ is completely pure and so is ____________________________________________ 100% water, it is hypotonic to all other solutions
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Osmosis and animal cells
When _____________________________________ then osmosis will take place E.g. osmosis in red blood cells Cells are placed in solutions of different concentrations Appearance of red blood cell Surrounding solution Explanation Isotonic Water enters and leaves the cell at the same rate hypotonic Water flows into the cell Cell swells and bursts This is called haemolysis hypertonic Water flows out of the cell Cell shrinks No net movement of water No change in appearance
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Osmosis in Plant Cells Appearance of plant cells Surrounding Solution
Explanation Isotonic Water enters and leaves the cell at the same rate No net movement of water No change in appearance Hypotonic Water flows into the cell and vacuole swells Cell wall prevents bursting Cell is turgid Hypertonic Water flows out of the cell and vacuole shrinks Membrane peels away from wall. Cell is plasmolysed
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Osmosis and Tissues Pieces of tissue e. g
Osmosis and Tissues Pieces of tissue e.g. potato cylinders can be placed in different solutions Appearance of potato cylinder Surrounding solution Description Isotonic _________________ ___________of cylinder Hypotonic _______________ than cylinder in isotonic solution Turgid Hypertonic ___________________ Than cylinder in isotonic solution Feels rubbery ________ Normal length, diameter And weight Longer, wider and heavier Shorter, thinner and lighter Flaccid
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Movement of water by Osmosis
Where two cells are touching and _____________ ________________________________________ ____________ The solutions inside have different concentrations water will move from one cell to another Cell A Cell B 5% solution 6% solution 94% water 95% water ______________________ cell __ to cell ____ Water will move from A B
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