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Regents Biology 2006-2007 Cell Membranes & Movement Across Them
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Regents Biology Cell (plasma) membrane Cells need an inside & an outside… separate cell from its environment cell membrane is the boundary IN food sugars proteins fats salts O 2 H 2 O OUT waste ammonia salts CO 2 H 2 O products cell needs materials in & products or waste out
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Regents Biology Building a membrane How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? What substance do you know that doesn’t mix with water? FATS LIPIDS oil & water don’t mix!!
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Regents Biology Lipids of cell membrane Membrane is made of phospholipids phospholipid bilayer “attracted to water” “repelled by water” inside cell outside cell phosphate lipid
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Regents Biology Semi-permeable membrane Need to allow passage through the membrane But need to control what gets in or out membrane needs to be semi-permeable So how do you build a semi-permeable membrane? aa H2OH2O sugarlipidsalt NH 3 So what needs to get across the membrane?
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Regents Biology Phospholipid bilayer What molecules can get through directly? inside cell outside cell fats & other lipids can slip directly through the phospholipid cell membrane, but… what about other stuff? lipid salt aa H2OH2O sugar waste
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Regents Biology Permeable cell membrane Need to allow more material through membrane needs to be permeable to… all materials a cell needs to bring in all waste a cell needs excrete out all products a cell needs to export out inside cell outside cell lipidsugaraa H2OH2O salt “holes”, or channels, in cell membrane allow material in & out waste
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Regents Biology outside cell Semi-permeable cell membrane But the cell still needs control membrane needs to be semi-permeable specific channels allow specific material in & out inside cell sugaraa H2OH2O salt waste
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Regents Biology How do you build a semi-permeable cell membrane? channels are made of proteins proteins both “like” water & “like” lipids bi-lipid membrane protein channels in bi-lipid membrane
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Regents Biology Protein channels Proteins act as doors in the membrane channels to move specific molecules through cell membrane
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Regents Biology Movement through the channel Why do molecules move through membrane if you give them a channel? ? ?
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Regents Biology Molecules move from high to low Diffusion move from HIGH to LOW concentration
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Regents Biology Diffusion Move from HIGH to LOW concentration “passive transport” no energy needed
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Regents Biology Simple Diffusion Move from HIGH to LOW inside cell outside cell Which way will fat move? low high fat
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Regents Biology Diffusion through a channel Move from HIGH to LOW inside cell outside cell sugar Which way will sugar move? low high sugar
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Regents Biology Diffusion Move from HIGH to LOW concentration through membrane simple diffusion no energy needed through a protein channel facilitated diffusion (with help) no energy needed high low
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Regents Biology Active transport Cells may need molecules to move against concentration difference need to pump “uphill” from LOW to HIGH using ATP protein pump requires energy ATP ATP
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Regents Biology Transport summary diffusion facilitated diffusion active transport ATP
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Regents Biology 2006-2007 Osmosis Movement of Water Across Cell Membrane
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Regents Biology Osmosis Water is very important, so we talk about water separately Osmosis diffusion of water from HIGH concentration of water to LOW concentration of water across a semi-permeable membrane
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Regents Biology Keeping water balance Cell survival depends on balancing water uptake & water loss freshwaterbalancedsaltwater
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Regents Biology http://www.dnatube.com/video/2775/Oni on-Cells-Plasmolysis http://www.dnatube.com/video/2775/Oni on-Cells-Plasmolysis
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Regents Biology Managing water balance Balanced conditions no difference between cell & environment example: blood problem: none water flows across membrane equally, in both directions volume of cell doesn’t change balanced
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Regents Biology Managing water balance Freshwater a cell in fresh water example: Paramecium problem: gains water, swells & can burst water continually enters Paramecium cell solution: contractile vacuole pumps water out of cell freshwater
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Regents Biology Controlling water Contractile vacuole in Paramecium
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Regents Biology Managing water balance Saltwater a cell in salt water example: shellfish problem: lose water plasmolysis in plants shrinking cell solution: take up water saltwater
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Regents Biology
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Active Transport
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Regents Biology Exocytosis
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Regents Biology Endocytosis
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Regents Biology Hypercholesterolemia Faulty LDL receptors in liver cells Liver does not remove Cholesterol builds up in blood vessels
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Regents Biology http://www.youtube.com/user/jchvatal1/ videos?view_as=public http://www.youtube.com/user/jchvatal1/ videos?view_as=public Go to mastering
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