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Transcript
Cell Membranes & Movement Across Them Biology 2006-2007 Cell (plasma) membrane Cells need an inside & an outside… separate cell from its environment ________________________________ IN OUT __________ __________ __________ __________ __________ __________ __________ __________ __________ __________ __________ __________ __________ __________ Biology cell needs materials in & products or waste out Building a membrane How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? _______ _______ Remember: oil & water don’t mix!! What substance do you know that doesn’t mix with water? Biology Lipids of cell membrane Membrane is made of special kind of lipid ______________________________ “split personality” “attracted to water” Membrane is a double layer ______________________________ phosphate inside cell lipid “attracted to water” Biology outside cell Semi-permeable membrane Cell membrane controls what gets in or out Need to allow some materials — but not all — to pass through the membrane _____________________________________ _________________________________________ So what needs to get across the membrane? sugar lipids Biology aa O2 H 2O salt waste Crossing the cell membrane What molecules can get through the cell membrane directly? ____________________________________ inside cell waste outside cell Biology lipid salt sugar aa H 2O but… what about other stuff? Cell membrane channels Need to make “doors” through membrane ______________________________________________ _____________________________________________________ H2O channel, salt channel, sugar channel, etc. inside cell waste Biology salt H 2O aa sugar outside cell How do you build a semi-permeable cell membrane? ___________________________________ proteins both “like” water & “like” lipids bi-lipid membrane Biology protein channels in bi-lipid membrane Protein channels Proteins act as doors in the membrane channels to move specific molecules through cell membrane HIGH LOW Biology Movement through the channel Why do molecules move through membrane if you give them a channel? high low Biology Molecules move from high to low ______________________________ Biology move from ______ to _______ concentration Diffusion Move from ______ to ______ concentration ______________________________ ______________________________ diffusion of water Biology diffusion diffusion of water Simple Diffusion Move from _______ to _______ fat inside cell outside cell fat fat fat fat Which way will fat move? fat fat fat fat Biology fat fat fat fat fat Diffusion through a channel Move from _______ to ________ sugar sugar sugar sugar inside cell sugar sugar Which way will sugar move? outside cell sugar Biology sugar sugar sugar sugar sugar sugar Diffusion Move from ______ to ______ concentration directly through membrane _____________________________ _____________________________ help through a protein channel _____________________________ _____________________________ high Biology low Simple vs. facilitated diffusion simple diffusion inside cell lipid facilitated diffusion inside cell H 2O protein channel outside cell Biology outside cell H 2O Active transport Cells may need molecules to move _________ concentration “hill” need to pump “uphill” from ________ to ________ using ATP _____________________________ _____________________________ __________ ATP Biology Transport summary facilitated diffusion facilitated diffusion active transport Biology ATP Osmosis Movement of Water Across Cell Membrane Biology 2006-2007 Osmosis Water is very important, so we talk about water separately _____________________ _____________________________________ _____________________________________ across a semi-permeable membrane Biology Keeping water balance Cell survival depends on balancing water uptake & water loss ____________ Biology ____________ ____________ Keeping right amount of water in cell ______________________ a cell in _____________________ high concentration of water around cell __________________________ example: ___________________ problem: ___________________ ___________________________ water continually enters Paramecium cell solution: _____________________ pumps water out of cell Biology freshwater Controlling water Contractile vacuole in Paramecium Biology Keeping right amount of water in cell saltwater ___________________ a cell in ________________ low concentration of water around cell _________________________ example: _______________ problem: _______________ _________________________ shrinking cell Biology solution: take up water Keeping right amount of water in cell ______________________ no difference in concentration of water between cell & environment _____________________ example: _____________ problem: none water flows across membrane equally, in both directions volume of cell doesn’t change Biology balanced
