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http://www.simpletruths.tv/store/movies.php?movie=race 2006-2007 Homeostasis Maintaining a balance of conditions within the cell (or organism). • maintaining pH (cells need pH of 6.8-7.2) pH Scale Acid Neutral Base 1 2 3 4 5 6 7 8 9 10 11 12 13 14 most cells Lab: pH and Buffers pH = potential hydrogen (meaning the ability of a solution to attract hydrogen ions) Acidic solution H+ H+ Basic solution OH- H+ H+ OHOH- OHH+ OH- Buffers and pH Virtual Activity http://www.mhhe.com/physsci/chemistry/essenti alchemistry/flash/buffer12.swf Homeostasis Maintaining a balance of conditions within the cell (or organism). • maintaining temperatures (humans 98.6oF) – shiver/sweat • metabolism = sum total of the body’s chemical activities High metabolism uses energy FAST Low metabolism uses energy SLOWLY Homeostasis (cont.) Maintaining a balance of conditions within the cell (or organism). maintaining blood sugar levels Person eats food containing glucose Blood sugar levels lower Blood sugar levels rise FEEDBACK: Insulin is released to control the incoming glucose and maintain blood sugar levels HSW: Simply Science: Equilibrium Diffusion SuperQuick Demo: Colored water into water. Move from HIGH to LOW concentration passive transport no energy needed Low Concentration High Concentration diffusion Concentration Gradient Higher concentration Na+ H2O(sodium) (water) of molecules. Lower concentration of molecules. Molecules move from high to low Diffusion (substances move) move from HIGH to LOW concentration across the concentration gradient. Concentration gradient Membrane High Low Cell Homeostasis Remember that the cell membrane controls what enters and leaves the cell IN OUT food - sugars - proteins - fats salts O2 H2O waste - ammonia - salts - CO2 - H2O products - proteins Cell needs materials in & products or waste out Remember… Membrane is made of special kind of lipid phospholipids “attracted to water” “split personality” Membrane is a double layer phospholipid bilayer phosphate inside cell lipid outside cell “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 semi-permeable (semi – partly) only some materials can get in or out So what needs to get across the membrane? sugar lipids aa O2 H 2O salt waste Crossing the cell membrane What molecules can get through the cell membrane without doors or help? fats and oils can pass directly through inside cell waste outside cell lipid salt sugar aa H 2O but… what about other stuff? Cell membrane protein 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 waste salt H 2O aa sugar outside cell Channels are made of proteins proteins both “like” water & “like” lipids bi-lipid membrane protein channels in bi-lipid membrane Protein channels (cont.) Proteins act as open doors in the membrane Concentration gradient channels to move specific molecules through cell membrane HIGH LOW Sugar molecules Movement through the channel Why do molecules move through the membrane if they find a channel? HIGH ? LOW ? Simple Diffusion Move from HIGH to LOW fat inside cell LOW fat fat fat fat fat Which way will these fat molecules move? HIGH outside cell fat fat fat fat fat fat fat fat 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 sugar sugar sugar sugar Simple vs. facilitated diffusion simple diffusion inside cell lipid facilitated diffusion LOW inside cell H 2O protein channel outside cell outside cell HIGH H 2O Active transport Cells may need to move molecules against concentration gradient need to pump “uphill” from LOW to HIGH using energy protein PUMP Requires ATP Notice the direction of Amino Acid movement and the concentrations! Na+ activates the pump. Low ATP High Quick Review… simple diffusion facilitated diffusion active transport ATP When Surface Area Counts: Intestinal Folds increase the surface area through which substances can pass. Villi = folds in the intestine that allow for more absorption area. What is the purpose of folds in the intestinal lining? Osmosis Osmosis and the Egg Demonstration Osmosis Water is so important that we discuss it separately Osmosis diffusion of water from high concentration of WATER to low concentration of water across a semi-permeable membrane Osmosis diffusion of water from high concentration of WATER to low concentration of water across a semi-permeable membrane High Low Keeping water balance (Homeostasis) Cell survival depends on balancing water uptake & water loss freshwater balanced saltwater Keeping right amount of water in cell Cells in Freshwater a cell in fresh water high concentration of water around cell cell gains water example: Paramecium problem: cells gain water, swell & can burst water continually enters Paramecium cell solution: contractile vacuole pumps water out of cell Hypotonic Controlling water Contractile vacuole in Paramecium Cells in Saltwater a cell in salt water low concentration of water around cell cell loses water example: shellfish problem: cell loses water plasmolysis in plants shrinking cell solution: take up water Hypertonic Cells in Balanced conditions no difference in concentration of water between cell & environment cell in equilibrium example: blood problem: none water flows across membrane equally, in both directions volume of cell doesn’t change Isotonic BLOOD! Animated Cell Responses to Solution Concentrations: http://www.phschool.com/science/biology_place/labbench/lab1/watpot.html Learning through Osmosis? Hands-On w/Virtual Lab 3: Diffusion of IKI through Selectively Permeable Membrane Virtual Lab 4: Osmosis thru a Selectively Permeable Membrane Virtual Lab 5: Onion Cell Plasmolysis DO NOT TOUCH LAB ITEMS! Cells need ENERGY to power biochemical reactions. How does a biochemical reaction work? Reactant Reactants ENTER the reaction. Endo – inside Exo – outside Reactant Energy is absorbed or released by the reaction. Products are PRODUCED by the reaction. EXOthermic Reaction = RELEASES energy Reactant Reactant Reactants ENTER the reaction. EXOTHERMIC Products are PRODUCED by the reaction. ENDOthermic Reaction = ABSORBS energy Reactant Reactant Reactants ENTER the reaction. ENDOTHERMIC Energy is ABSORBED by the reaction. Products are PRODUCED by the reaction. Exothermic Reaction = Releases Energy ACTIVATION ENERGY = energy required ENERGY to cause the reaction to occur. Energy RELEASED TIME Endothermic Reaction = Absorbs Energy ACTIVATION ENERGY = energy required ENERGY to cause the reaction to occur. Energy ABSORBED TIME Any Questions?