Cell Membranes & Movement Across Them - Regents Biology PDF 2006-2007

Cell Membranes & Movement Across Them Regents Biology 2006-2007 A Nuclear envelope Cortex ---... Eubacteria Plasma membrane Early endosome... Archaebacteria...

Cell Membranes & Movement Across Them Regents Biology 2006-2007 A Nuclear envelope Cortex ---... Eubacteria Plasma membrane Early endosome... Archaebacteria Regents Biology  Cell (plasma) membrane  Cells need an inside & an outside…  separate cell from its environment  cell membrane is the boundary IN OUT food waste - sugars - ammonia - proteins - salts - fats - CO2 salts - H2O O2 products H2O - proteins Regents 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? 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  phospholipids  “split personality” “attracted to water”  Membrane is a double layer  phospholipid bilayer phosphate inside cell lipid “repelled by water” Regents 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  semi-permeable  only some material can get in or out So what needs to get across the membrane? sugar lipids aa O2 H2O salt waste Regents Biology  Crossing the cell membrane  What molecules can get through the cell membrane directly?  fats and oils can pass directly through lipid inside cell waste salt but… sugar aa H2O what about outside cell other stuff? Regents Biology  Cell membrane channels  Need to make “doors” through membrane  protein channels allow substances in & out  specific channels allow specific material in & out  H2O channel, salt channel, sugar channel, etc. inside cell H2O aa sugar salt wasteBiology Regents outside cell  How do you build a semi-permeable cell membrane?  Channels are made of proteins  proteins both “like” water & “like” lipids bi-lipid protein channels membrane in bi-lipid membrane Regents Biology  Protein channels  Proteins act as doors in the membrane  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? ? HIGH ? LOW Regents Biology  Molecules move from high to low  Diffusion  move from HIGH to LOW concentration Regents Biology  Diffusion  Move from HIGH to LOW concentration  passive transport  no energy needed diffusion of water Regents Biology diffusion osmosis  Simple Diffusion  Move from HIGH to LOW fat fat fat Which way inside cell will fat move? fat fat fat LOW HIGH fat outside cell fat fat fat fat fat fat fat Regents Biology  Facilitated Diffusion  Move from HIGH to LOW through a channel sugar sugar sugar sugar inside cell sugar sugar LOW Which way will sugar move? HIGH outside cell sugar sugar sugar Regents Biologysugar sugar sugar sugar  Diffusion  Move from HIGH to LOW concentration  directly through membrane  simple diffusion  no energy needed  help through a protein channel  facilitated diffusion (with help)  no energy needed HIGH Regents Biology LOW  Simple vs. facilitated diffusion simple diffusion facilitated diffusion lipid inside cell inside cell H2O protein channel H2O outside cell outside cell Regents Biology  Active transport  Cells may need molecules to move against concentration “hill”  need to pump “uphill”  from LOW to HIGH using energy  protein pump  requires energy  ATP ATP Regents Biology  Transport summary simple diffusion facilitated diffusion active ATP transport Regents Biology  Osmosis Movement of Water Across Cell Membrane Regents Biology 2006-2007  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 Regents Biology  Keeping water balance  Cell survival depends on balancing water uptake & water loss freshwater balanced saltwater Regents Biology 1 Keeping right amount of water in cell  Freshwater freshwater KABOOM!  a cell in fresh water  high concentration of water around cell  cell gains water  example: Paramecium  problem: cells gain water, swell & can burst No problem,  water continually enters here Paramecium cell  solution: contractile vacuole  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, saltwater I’m shrinking!  a cell in salt water  low concentration of water around cell  cell loses water  example: shellfish  problem: cell loses water I will  in plants: plasmolysis survive!  in animals: shrinking cell  solution: take up water Regents Biology 3 Keeping right amount of water in cell  Balanced conditions That’s balanced  no difference in better! concentration of water between cell & environment  cell in equilibrium  example: blood  problem: none  water flows across I could be better… membrane equally, in both directions  volume of cell doesn’t change Regents Biology  Ice Fishing in Barrow Regents Biology