Cell Membranes Movement Across Them Regents Biology 2006
Cell Membranes & Movement Across Them Regents Biology 2006 -2007
Cell Membrane Video Regents Biology
Cell (plasma) membrane § Cells need an inside & an outside… u separate cell from its environment u cell membrane is the boundary IN food - sugars - proteins - fats salts O 2 H 2 O Regents Biology OUT waste - ammonia - salts - CO 2 - H 2 O products - proteins cell needs materials in & products or waste out
Without a cell membrane Regents Biology
Building a membrane § How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? FATS LIPIDS Remember: oil & water don’t mix!! What substance do you know that doesn’t mix with water? Regents Biology
Lipids of cell membrane § Membrane is made of special kind of lipid u u phospholipids “split personality” Hydrophilic “attracted to water” § Membrane is a double layer u phospholipid bilayer phosphate inside cell lipid Hydrophobic outside cell Regents Biology “repelled by water”
Semi-permeable membrane § Cell membrane controls what gets in or out § Need to allow some materials — but not all — to pass through the membrane u semi-permeable § only some material can get in or out So what needs to get across the membrane? sugar lipids Regents Biology aa O 2 H 2 O salt waste
Crossing the cell membrane § What molecules can get through the cell membrane directly? u fats and oils can pass directly through inside cell waste outside cell Regents Biology lipid salt sugar aa H 2 O but… what about other stuff?
Cell membrane channels § Need to make “doors” through membrane u protein channels allow substances in & out § specific channels allow specific material in & out § H 2 O channel, salt channel, sugar channel, etc. inside cell salt waste. Biology Regents H 2 O aa sugar outside cell
How do you build a semi-permeable cell membrane? § Channels are made of proteins § a. k. a. Protein Channels u proteins both “like” water & “like” lipids bi-lipid membrane Regents Biology protein channels in bi-lipid membrane
Protein channels § Proteins act as doors in the membrane u channels to move specific molecules through cell membrane HIGH LOW Regents Biology
Movement through the channel § Why do molecules move through membrane if you give them a channel? § Certain molecules are moved to create a balance HIGH ? LOW ? Regents Biology
Cell Membrane = Fluid Mosaic § Fluid: u The cell membrane isn’t rigid. proteins embedded within it move around as well § Mosaic: u It is comprised (made up) of many different substances § Lipids, proteins, glycoproteins, Regents Biology etc…
Regents Biology
Cell Membrane Rap Regents Biology
Molecules move from high to low § Diffusion u move from HIGH to LOW concentration Regents Biology
Diffusion § Move from HIGH to LOW concentration passive transport u no energy needed u Regents Biology diffusion of water osmosis
Simple Diffusion § Move from HIGH to LOW fat inside cell LOW fat fat fat HIGH outside cell fat Regents Biology fat fat fat Which way will fat move? fat
Facilitated Diffusion § Move from HIGH to LOW through a channel sugar inside cell sugar LOW Which way will sugar move? HIGH outside cell sugar Regents Biologysugar sugar
Diffusion § Move from HIGH to LOW concentration u directly through membrane § simple diffusion § no energy needed u help through a protein channel § facilitated diffusion (with help) § no energy needed HIGH Regents Biology LOW
Simple vs. facilitated diffusion simple diffusion inside cell lipid facilitated diffusion inside cell H 2 O protein channel outside cell Regents Biology outside cell H 2 O
Active transport § Cells may need molecules to move against concentration “hill” u need to pump “uphill” § from LOW to HIGH using energy protein pump u requires energy § ATP u ATP Regents Biology
Transport summary simple diffusion facilitated diffusion active transport Regents Biology ATP
Osmosis Movement of Water Across Cell Membrane Regents Biology 2006 -2007
Osmosis § Water is very important, so we talk about § water separately Osmosis u diffusion of water from HIGH concentration of water to LOW concentration of water § across a semi-permeable membrane Regents Biology
Keeping water balance § Cell survival depends on balancing water uptake & water loss freshwater Regents Biology balanced saltwater
1 Keeping right amount of water in cell § Freshwater KABOOM! freshwater a cell in fresh water u high concentration of water around cell u § cell gains water § example: Paramecium § problem: cells gain water, swell & can burst w water continually enters No problem, here Paramecium cell § solution: contractile vacuole w pumps water out of cell Regents Biology
Controlling water § Contractile vacuole in Paramecium Regents Biology
2 Keeping right amount of water in cell § Saltwater I’m shrinking, I’m shrinking! a cell in salt water u low concentration of water around cell u § cell loses water example: shellfish u problem: cell loses water u § in plants: plasmolysis § in animals: shrinking cell u solution: take up water Regents Biology I will survive! saltwater
3 Keeping right amount of water in cell § Balanced conditions u That’s better! no difference in concentration of water between cell & environment § cell in equilibrium § example: blood § problem: none I could w water flows across membrane equally, in both directions w volume of cell doesn’t change Regents Biology be better… balanced
Ice Fishing in Barrow Regents Biology
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