2Cell (plasma) membrane Cells need an inside & an outside…separate cell from its environmentcell membrane is the boundaryINfood- sugars- proteins- fatssaltsO2H2OOUTwaste- ammonia- salts- CO2- H2Oproducts- proteinscell needs materials in & products or waste out
3Lipids of cell membrane Membrane is made of special kind of lipidphospholipids“split personality”Membrane is a double layerphospholipid bilayer“attracted to water”phosphateinside celloutside celllipid“repelled by water”
4Semi-permeable membrane Cell membrane controls what gets in or outNeed to allow some materials — but not all — to pass through the membranesemi-permeableonly some material can get in or outSo what needs to get across the membrane?sugarlipidsaaO2H2Osaltwaste
5Cell membrane channels Need to make “doors” through membraneprotein channels allow substances in & outspecific channels allow specific material in & outH2O channel, salt channel, sugar channel, etc.inside cellH2Oaasugarsaltoutside cellwaste
6Protein channels Proteins act as doors in the membrane channels to move specific molecules through cell membraneHIGHDonuts!Each transport protein is specific as to the substances that it will translocate (move).For example, the glucose transport protein in the liver will carry glucose from the blood to the cytoplasm, but not fructose, its structural isomer.Some transport proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane -- simply provide corridors allowing a specific molecule or ion to cross the membrane.These channel proteins allow fast transport.For example, water channel proteins, aquaprorins, facilitate massive amounts of diffusion.LOW
7Molecules move from high to low Diffusionmove from HIGH to LOW concentrationMovement from high concentration of that substance to low concentration of that substance.
8Diffusion Move from HIGH to LOW concentration diffusion of water passive transportno energy neededdiffusion of waterdiffusionosmosis
9Diffusion Move from HIGH to LOW concentration directly through membranesimple diffusionno energy neededhelp through a protein channelfacilitated diffusion (with help)HIGHLOW
11Active 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
12Transport summary simple diffusion facilitated diffusion ATPactive transport
14Osmosis 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
15Keeping right amount of water in cell 1Keeping right amount of water in cellHypotonic conditiona cell in distilled waterhigh concentration of water around cellcell gains waterproblem: cells gain water, swell & can burstPlant cells- become turgid, which which is normalAnimal cells-burst and dieKABOOM!freshwaterNo problem, here
16Keeping right amount of water in cell 2Keeping right amount of water in cellIsotonic conditionno difference in concentration of water between cell & environmentWater flows equally into and out of cellcell in equilibriumPlant cells: FlaccidAnimal cells: NormalThat’s better!balancedI could be better…
17Keeping right amount of water in cell 3Keeping right amount of water in cellHypertonic solutiona cell in salt waterlow concentration of water around cellcell loses waterPlant cells- shrink, can survive for a timeAnimal cells- shrinkand dieI’m shrinking, I’m shrinking!saltwaterI will survive!