Osmosis and Diffusion

The Cell MembraneStructure and FunctionCell Membrane FunctionsCell membrane surrounds the cell, regulating the transport of materials into and out of the cell

Cell Membrane StructureLipid Bilayer: a double layer of phospholipids that make up the cell membrane

PhospholipidPhosphate Head:PolarHydrophilic (attracted to water)Two Fatty Acid Tails:NonpolarHydrophobic (avoids water)

Two LayersOutsides: Polar HeadsInside: Nonpolar Tails

Other lipids ?Lipids Fatty acids Fats and waxesSteroidsCholesterolTestosteronePhospholipids

Cell Membrane StructurePhospholipids are arranged so hydrophilic (water loving) ends face outside and hydrophobic (water fearing) tails create the interior

Cell Membrane StructurePhospholipid BilayerTransmembrane ProteinsCholesterol (a steroid)Glycoprotein and Carbohydrate

Cell Membrane StructureTransmembrane ProteinsJob:Attachment point for one cell to attach to a neighborAnchor cell in placeCreate channels for large and/or polar molecules to pass

Cell Membrane StructureCholesterolJob:Maintains fluidity of cell membrane

Cell Membrane StructureGlycolipids and CarbohydratesJob:Serve as cell markers for identification

Cell Membrane Structure The Fluid Mosaic ModelThe membrane is dynamic molecules are constantly movingVideo Link

Selectively PermeableThe cell membrane is selectively permeable, meaning some substances can pass through the cell membrane, but others cant!Permeable is the ability for something to pass through

Bell Ringer-2/23/15Use the paper on your desk to name the circled parts of the cell membrane:

FPassive TransportOsmosis and DiffusionRaisin demonstration needs to be set up first to allow time for osmosis to take place. 14Selectively PermeableThe cell may transport substances Passive Transport: No Energy required Active Transport: Uses energy (ATP)

Passive TransportMovement of a substance into/out of a cell without using energyHIGH LOW concentration3 TypesSimple DiffusionFacilitated DiffusionOsmosis

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About ConcentrationWe just learned that substances move from HIGHLOW concentration in passive transportbut what do we mean by concentration?Means amount dissolved in a containerHow do you like your sweet tea? a. Unsweet (low concentration of sugar)b. Sweet c. Super sweet(high concentration of sugar)

Solute = Substance dissolved in water

The sugar is dissolved at different concentrations. Unsweet tea has a low concentration of sugar, and super sweet tea has a high concentration of sugar.17Concentration GradientsA concentration gradient is the difference in the concentration, or amount, of something in a spaceIn the box below, the dots have a higher concentration on the left than the right, so they begin movement to the right

When the concentration gradient is the same throughout the area, it is in a dynamic equilibriumParticles are moving from one side to the other, but at the same rate.

Picture: www.hartnell.eduAfter this slide, lead into the food coloring discussion. Have them write down observations after they add food coloring to water. Then do diffusion slide and ask them to observe the water again. They should be able to reach the conclusion that the food coloring is diffusing to create equilibrium. The students can stir the water to help equilibrium be reached faster. 18Passive Transport: DiffusionDiffusion is when a substance moves from an area of high concentration to low concentration areaDiffusion will continue until balanced/equal at equilibriumIn this case, small, nonpolar particles cross through the membrane Food Coloring Demo!

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Facilitated DiffusionLarge molecules require special protein channels to move throughEx. Ions, glucoseVideo Link

Passive Transport: OsmosisOsmosis is the diffusion of water across a selectively permeable membraneWater moves from an area of high concentration (lots of water) to low concentration (little water)Passive Transport: Water moves with its concentration gradientNo energy is required

Picture: scienceaid.co.uk

About OsmosisWater can move into or out of the cell, depending on the environment (solution) that the cell is inSolvent + Solute = SolutionSolvent does the dissolving (ex. Water)Solute substance dissolved(ex. Salt)Describing SolutionsIsotonic Solutionsame or equalHypertonic Solutionabove/over/higherHypotonicSolutionbelow/under/lowerEQUAL amounts of solute in/out of cell.HIGHER solute outside.LOWER solute outside.

How Osmosis WorksIsotonicsame or equalHypertonicabove/over/higherHypotonicbelow/under/lowerWater in/out.

Plant CellsFlaccid, Central Vac. not full

Animal Cell**No Change to cellWater out

Plant CellsPlasmolysis, Cell death

Animal CellDehydration, Cell shrivels

Water in.

Plant Cells**Turgid, Central Vac. Full

Animal CellLysed, Cell bursts

OsmosisOnion in Salt WaterBlood Cells Take a look at the raisins on your deskwhats happening?

Picture: www.peoi.orgSame Swelling ShrinkingIf time permitting, discuss the pH of blood at 7.3 norm. The blood cells have a buffer that tries to regulate the cell at 7.3. If something happens that makes it too acidic or basic, the buffers can fail and cause problems. In the case of the fish, the pH became to high in the water for them to handle. Diffusion caused water to swell and rupture their cells, thus causing them to die. Fish generally have higher solute concentration inside their bodies, and the drastic change in pH alters this and affects them negatively. 26Check for understandingAfter an ice storm, road crews salt the roadways to melt ice and increase traction for cars. What happens to the plants on the side of the road? Explain why.Isotonic, Hypotonic, or Hypertonic?CELL

10% NaCL90 % H2O10% NaCL Environment90 % H2OWater Goes?Isotonic-Water goes in/out (balanced); cell stays the same!CELL

10% NaCL90 % H2O10% NaCL Environment90 % H2OIsotonic, Hypotonic, or Hypertonic?CELL

20% NaCL80 % H2O10% NaCL Environment90 % H2OWater Goes?Hypotonic-water goes IN! Cell swells!CELL

20% NaCL80 % H2O10% NaCL Environment90 % H2OIsotonic, Hypotonic, or Hypertonic?CELL

5% NaCL

10% NaCL Environment

Water Goes?Hypertonic-water goes OUT-Cell Shrinks!!CELL

5% NaCL

10% NaCL Environment

Often, you will just be given the solute concentration in the environment. What is the water concentration? Would it move in or out?Bellringer-3/2/15Define Diffusion. Give an example.Define Osmosis. Give an example. What are the three solutions relating to osmosis? Describe whether they make the cell shrink, swell, or stay the same. Passive transport (such as diffusion and osmosis) is the movement of molecules from:An area of high concentration to an area of low concentrationAn area of low concentration to an area of high concentrationAn area of equilibrium to an area of high concentrationAll of the aboveOsmosis and Diffusionhttps://www.youtube.com/watch?v=IaZ8MtF3C6MBellringer-3/3/15Identify the solution as iso, hyper, or hypotonic and draw arrows labeling the direction of water movement.

A cell is placed into a salt solution. The salt concentration is greater in the solution than inside the cell. Which describes what will most likely happen?Water will flow into the cell by active transportWater will flow into the cell by passive transportWater will flow out of the cell by active transportWater will flow out of the cell by passive transport

85% H2O15% solute80% H2O20 % solute70% H2O

70% H2O

40% solute30% soluteActive TransportMovement Requiring EnergyActive TransportMolecules move across the membrane AGAINST their concentration gradientMoving LOW to HIGHENERGY is required! (imagine trying to push your way through a crowd vs. going with the flow)Two TypesProtein PumpsBulk Transport

Protein PumpsTransport small molecules/ions AGAINST their concentration gradients (LOW HIGH)Uses ATP (cell energy)

Notice the ATPBulk TransportLarger molecules (proteins, starch) are transported by vesicles that merge with the cell membraneExocytosis-contents leaving the cell through the membraneEndocytosis-contents entering in vesicles (pinocytosis and phagocytosis)

HomeostasisMaintaining BalanceHomeostasisThe process by which an organisms internal environment is kept in equilibrium (stable) in spite of changes in the external environmentExamples:Internal Temperature Sweating removes excess body heatShivering increases heat productionWater balance Kidneys adjust water amount in urine A physical response to stress Breathing/heart rate increasesPupils dilateSweating)

HomeostasisHomeostasis requires energyFor active transport to deliver needed moleculesT0 rid cell of toxins To move to avoid danger or find food

Homeostasis in CellsCells can maintain homeostasis in a number of waysControlling substances that cross the membraneActive and Passive transport)

Homeostasis in CellsCells can maintain homeostasis in a number of waysBuffersCells produce buffers to help maintain a constant pH. Examples:Human blood cells must maintain a pH of 7.35-7.45Cells in stomach maintain a pH of 3Cells in Small Intestine maintain a pH of 6What is a buffer?A chemical that can raise or lower the pH(it can behave like an acid or a base)

HomeostasisMaintenance of homeostasis is vital for life!https://www.youtube.com/watch?v=6fhbbFd4icY

Bellringer-2/25/15If energy is needed to move materials into or out of a cell, what is most likely occurring?Active transportPassive transportOsmosisDiffusionDuring strenuous exercise, the body temperature increases. The body responds to the increase in temperature by sweating, which helps to reduce the body temperature. Which is demonstrated in this situation?ExcretionMetabolismHomeostasisSynthesis Which of the following serves as the cells boundary from its environment?MitochondriaCell membraneChloroplastChannel proteinWhich of the following is a function of the cell membrane?Breaks down lipids, carbohydrates, and proteins in the bodyStores water, salt, proteins, and carbohydratesKeeps the cell wall in placeRegulates which materials enter and leave the cellThe cell membrane contains channels and pumps that help move materials from one side to the other. What are these channels and pumps made of?CarbohydratesLipidsBilipidsProteins

Diffusion is the movement of molecules from:An area of low concentration to an area of high concentrationAn area of high concentration to an area of low concentrationAn area of equilibrium to an area of high concentrationAll of the aboveDiffusion occurs because:Molecules constantly move and collide with each otherThe concentration of a solution is never the same throughout a solutionThe concentration of a solution is always the same throughout a solutionMolecules never move or collide with each otherWhen the concentration of molecules on both sides of the membrane is the same, the molecules will:Move across the membrane to the outside of the cellStop moving across the membraneMove across the membrane in both directionsMove across the membrane to the inside of the cellThe diffusion of water across a selectively permeable membrane is called:Osmotic pressureOsmosisFacilitated diffusionActive transportAn animal cell that is surrounded by fresh water will burst because the osmotic pressure causes:Water to move into the cellWater to move out of the cellSolutes to move into the cellSolutes to move out of the cellWhich means of particle transport requires input of energy from the cell?DiffusionOsmosisFacilitated DiffusionActive Transport