Presentation on theme: "Have your Cell Division packet on edge of desk! Thanks!"— Presentation transcript:
1 Have your Cell Division packet on edge of desk! Thanks! Learning Goal:1) I can explain the process of diffusion & osmosis and how it’s important to cells.Thinking Skills:Problem solving, main ideaHabits of Mind:persistingHave your Cell Division packet on edge of desk! Thanks!Computers ON!Agenda: Feb 13 , 2015ET #51: Why do you smell odors when you are not necessarily right next to the source?Review Cell DivisionExplain 28: Osmosis Activity https://www.youtube.com/watch?v=SSS3EtKAzYchttps://www.youtube.com/watch?v=SrON0nEEWmo4) Homework: Complete Osmosis HW? Test Review due Tuesday/ Wednesday after break. Test 2/26 & 2/27; SCaR-NONE
2 ET #51: Why do you smell odors when you are not necessarily right next to the source? good ppt of osmosis/diffusion
5 Scientifically speaking, what’s wrong with this Garfield picture? Let’s quickly and quietly get a RED pen out and log on to the computer.Go to the public/all/kmchenry folder and grade your Cell Division paper, making corrections as needed. You have SEVEN minutes! Work quickly!
17 12. What is the “Big Idea” here? Water moves into or out of the eggs depending on the concentration of water inside vs. outside.= moves from High to Low
18 Saltwater is the solution, Salt is the solute Water is the solvent Solute: “The dissolved substance in a solution”Example: SaltwaterSaltwater is the solution,Salt is the soluteWater is the solventDraw different solutes by using different symbols.Example:= water= sugar= salt
33 One solution has a lower concentration of solute than another. Both solutions have same concentrations of solute.One solution has a higher concentration of solute than another.
34 There are microscopic pores in the membrane. 5There are microscopic pores in the membrane.Molecules below a certain size can diffusethrough the pores.Water molecules can easily diffuse throughthe pores.In the next slidesrepresents a water moleculeandrepresents a sugar molecule
35 membrane water sugar solution 6 There are as many water molecules on the right as there are on the left but many of them are attached to sugar molecules and are not free to move.
36 Because there are more freely moving water molecules on 7Sugar molecules can pass through the membrane but, being surrounded by a cloud of water molecules, they move more slowly.Because there are more freely moving water molecules onthe left, more diffuse through the pores of the membrane fromleft to right than from right to left.Molecular movement
38 Because the membrane allows only molecules 9Because the membrane allows only moleculesof a certain size to diffuse through it, it iscalled selectively permeable.The cell membrane functions as a selectivelypermeable membrane.The cell sap and cytoplasm function asfairly concentrated solutions.
39 The scale of the following drawings is greatly distorted. Scale of drawings10The scale of the following drawings is greatly distorted.Even if the cells were as large as they appear on the screen, the molecules would still be invisible particles
40 Osmosis in animal cells 11so water diffuses into the cellby osmosisThere is a greater concentration of free water molecules outside the cell than insideand the cell swells up
41 If osmosis continued the animal cell would burst 12If osmosis continued the animal cell wouldburstThis would be bad news for animalsConsequently there are processes in theanimal’s body which control osmosisMainly, this is done by keeping theconcentration of body fluids outside the cellthe same as it is inside
42 As a result the fish takes in water by osmosis Fresh water fish14TroutIn fresh water fish, the blood is more concentrated than the surrounding waterAs a result the fish takes in water by osmosisNot so much through the skin, which is thick,but through the gills which have a very thinmembrane
43 The fish gets rid of the excess water by means of its kidneys 14PerchThe fish gets rid of the excess water by means of its kidneyskidneys expelexcess water ...blood carries waterto kidneysgills absorb water by osmosis...in the form ofdilute urineheart
44 Sea water is a more concentrated solution than the Sea water fish15HerringSea water is a more concentrated solution than thefish’s blood. What will be the osmotic effect ?A sea water fish will lose water by osmosis throughits gills.Sea water fish related to sharks, e.g. dogfish, avoid losing water to their surroundings by maintaining their blood at the same concentration as sea waterThe fish drinks sea water and the gills expel theexcess salt from the blood, so keeping itsconcentration constant
45 The vacuole will expand, pushing the cytoplasm 16In a plant cell, the cell membrane acts as aselectively permeable membraneThe cell wall is freely permeable to waterThe vacuole contains a solution of salts and sugarsIf there is water outside the cell, it will diffuseby osmosis into the vacuoleThe vacuole will expand, pushing the cytoplasmoutwards against the cell wall
46 The cellulose cell wall cannot stretch, so the 17The cellulose cell wall cannot stretch, so thevacuole cannot continue to expandBut the pressure of the vacuole against the cellwall makes the cell very firmA plant cell in this condition is said to be turgidIf all the cells in the plant are turgid, the plant willbe firm and upright and the leaves would beexpanded
47 Plant cells cell wall vacuole cytoplasm and cell membrane 18cell wallvacuolecytoplasm andcell membraneA useful analogy is the bicycle tyre. The outer casing represents the cell wall; the inner tube represents the cytoplasm and the air inside represents the vacuole. When the tyre is pumped up, the air pressure pushes the inner tube against the outer casing. The outer casing cannot expand and so the pressure in the tube builds up until the tyre is firmThe cell absorbs waterby osmosis ........but the cell wall stops thecell expanding any more
48 Limp and turgid tissue21These cells are short of water; the tissue is limp and the plant is wiltingThe cells have taken upwater by osmosis; thecells are turgid and thetissue is firm
49 Busy Lizzie (1) wilting (2) recovering (3) recovered 22 (1) Wilting. The plant is short of water. The leaf cells are no longer turgid and the leaves curl up and droop.(3) Recovered. Water is once more available. The leaf cells take up water by osmosis and become turgid. The leaves are now firm and are held horizontally.Woody plants such as trees and shrubs do not collapse when they wilt but their leaves become limp.