Presentation on theme: "Section Objectives Explain how the processes of diffusion, passive transport, and active transport occur and why they are important to cells. Predict the."— Presentation transcript:
1 Section ObjectivesExplain how the processes of diffusion, passive transport, and active transport occur and why they are important to cells.Predict the effect of a hypotonic, hypertonic, or isotonic solution on a cell.
2 Movement through the channel Why do molecules move through membrane if you give them a channel?HIGH?LOW?
3 Molecules move from high to low Diffusionmove from HIGH to LOW concentrationMovement from high concentration of that substance to low concentration of that substance.
4 Diffusion Move from HIGH to LOW concentration diffusion of water passive transportno energy neededdiffusion of waterdiffusionosmosis
5 Simple Diffusion Move from HIGH to LOW LOW HIGH fat fat fat Which way will fat move?inside cellfatfatfatLOWHIGHfatoutside cellfatfatfatfatfatfatfat
6 Facilitated Diffusion Move from HIGH to LOW through a channel (has a helper)sugarsugarsugarsugarinside cellsugarsugarLOWWhich way will sugar move?HIGHoutside cellsugarsugarsugarsugarsugarsugarsugar
7 Diffusion Move from HIGH to LOW concentration directly through membranesimple diffusionno energy neededhelp through a protein channelfacilitated diffusion (with help)HIGHLOW
9 Osmosis: Diffusion of Water The diffusion of water across a selectively permeable membrane is called osmosis.Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.
10 Osmosis Water is very important, so we talk about water separately diffusion of water from HIGH concentration of water to LOW concentration of wateracross a semi-permeable membrane
11 What controls osmosis?Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis.AfterOsmosisBeforeOsmosisSelectively permeable membraneWater moleculeSugar molecule
12 Keeping water balanceCell survival depends on balancing water uptake & water lossfreshwaterbalancedsaltwater
13 Osmosis is the passive transport of water In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentrationHypertonic: [hyper=above, over]Solutions in which more solute present (concentrated solution)Hypotonic: [hypo= below, under]Solutions in which less solute is present (dilute solution)Isotonic: [ iso= equal]Solutions have equal concentrations of substances
14 Cells in an isotonic solution (= concentrations)the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell.H2OH2OWater MoleculeDissolved Molecule
15 Cells in an isotonic solution water molecules move into and out of the cell at the same rate, and cells retain their normal shape.H2OH2OWater MoleculeDissolved Molecule
16 Cellular Structure and Function Isotonic SolutionWater and dissolved substances diffuse into and out of the cell at the same rate.Plant CellBlood Cell11,397x
17 Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution.
18 Keeping right amount of water in cell Balanced conditions (isotonic)no difference in concentration of water between cell & environmentcell in equilibriumexample: bloodproblem: nonewater flows across membrane equally, in both directionsvolume of cell doesn’t changeThat’s better!balancedI could be better…
19 Cells in a hypotonic solution hypotonic solution: dilute solution thus low solute concentrationIn a hypotonic solution, water enters a cell by osmosis, causing the cell to swell.H2OH2OWater MoleculeDissolved Molecule
20 Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases. (plants prefer this –it makes the leaves firm)
21 Keeping right amount of water in cell Freshwater -Hypotonica cell in fresh waterhigh concentration of water around cellcell gains waterexample: Parameciumproblem: cells gain water, swell & can burstwater continually enters Paramecium cellsolution: contractile vacuolepumps water out of cellKABOOM!freshwaterNo problem, here
22 Controlling waterContractile vacuole in Paramecium
23 Cells in a hypertonic solution concentrated solution, thus a high solute concentrationIn a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrinkH2OH2OWater MoleculeDissolved Molecule
24 Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall. PLASMOLYSIS
25 Solute concentration is higher outside the cell. Cellular Structure and FunctionHypertonic SolutionSolute concentration is higher outside the cell.Water diffuses out of the cell.Plant CellBlood Cell13,000x
26 Keeping right amount of water in cell Saltwater -Hypertonica cell in salt waterlow concentration of water around cellcell loses waterexample: shellfishproblem: cell loses waterin plants: plasmolysisin animals: shrinking cellsolution: take up waterI’m shrinking, I’m shrinking!saltwaterI will survive!
27 Passive TransportWhen a cell uses no energy to move particles across a membrane passive transport occursParticles go DOWN their concentration gradient.all diffusion & osmosis are passive transport.Plasma membraneConcentration gradient
28 Active Transportactive transport :Movement of materials through a membrane against a concentration gradient and requires energy from the cell. ATPCellular energyCarrier proteinsPlasma membraneConcentration gradientCellular energy
29 Active transportCells may need molecules to move against concentration “hill”need to pump “uphill”from LOW to HIGH using energyprotein pumprequires energyATPPlants have nitrate & phosphate pumps in their roots.Why?Nitrate for amino acidsPhosphate for DNA & membranesNot coincidentally these are the main constituents of fertilizer.ATP
30 How active transport occurs a transport protein called a carrier protein first binds with a particle of the substance to be transported.Each type of carrier protein has a shape that fits a specific molecule or ion.
31 Exocytosis and endocytosis transport large molecules uses energy Exocytosis [ exo = outside]movement of large materials OUT of the cell~a vesicle may fuse with the membrane and expel its contentsFLUID OUTSIDE CELLCYTOPLASM
32 movement of large materials to INSIDE of the cell 2. Endocytosis [ endo = inside]movement of large materials to INSIDE of the cell~membrane may fold inward, trapping materials from the outside