Goal 2.03: The Cell as a Living System

1. Goal 2.03: The Cell as a Living System http://www.simpletruths.tv/store/movies.php?movie=race

2. Homeostasis Maintaining a balance of conditions within the cell (or organism). • maintaining pH (cells need pH of 6.8-7.2) pH Scale Soap Lemon juice Neutral Base Acid 1 2 3 4 5 6 7 8 9 10 11 12 13 14 most cells Hydrogen peroxide Vinegar

3. Lab: pH and Buffers pH = potential hydrogen (meaning the ability of a solution to attract hydrogen ions) Acidic solution Basic solution H+ OH- H+ OH- H+ OH- H+ OH- H+ OH- Buffers and pH Virtual Activity http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/buffer12.swf

4. 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 Metabolic Rate:how fast an organism uses up its stored energy. Low metabolism uses energy SLOWLY

5. Homeostasis (cont.) Maintaining a balance of conditions within the cell (or organism). maintaining blood sugar levels HSW: Simply Science: Equilibrium

6. Diffusion SuperQuick Demo: Colored water into water. • Move from HIGH to LOW concentration • passive transport • no energy needed Low Concentration High Concentration diffusion

7. Concentration Gradient Higher concentration of molecules. H2O (water) Na+ (sodium) Molecules will always go from high to low. Lower concentration of molecules.

8. Molecules move from high to low • Diffusion (substances move) • move from HIGH to LOW concentration across the concentration gradient. Membrane High Concentration gradient Low

9. Cell Homeostasis • Remember that the • cell membrane controls what enters and leaves the cell IN food - sugars - proteins - fats salts O2 H2O OUT waste - ammonia - salts - CO2 - H2O products - proteins Cell needs materials in & products or waste out

10. inside cell outside cell Remember… • Membrane is made of special kind of lipid • phospholipids • “split personality” • Membrane is a double layer • phospholipid bilayer “attracted to water” phosphate lipid “repelled by water”

11. Semi-permeablemembrane • 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? lipids aa O2 H2O salt sugar waste

12. inside cell outside cell Crossing the cell membrane • What molecules can get through the cell membrane without doors or help? • fats and oils can pass directly through lipid salt waste but… what about other stuff? sugar aa H2O

13. 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 H2O aa sugar salt outside cell waste

14. Channels are made of proteins • proteins both “like” water & “like” lipids bi-lipid membrane protein channelsin bi-lipid membrane

15. Protein channels (cont.) • Proteins act as opendoors in the membrane • channels to move specific molecules through cell membrane HIGH Sugar molecules Concentration gradient LOW

16. Movement through the channel • Why do molecules move through the membrane if they find a channel? HIGH ? LOW ?

17. Simple Diffusion Which way will these fat molecules move? fat • Move from HIGH to LOW fat fat inside cell fat fat fat LOW HIGH fat outside cell fat fat fat fat fat fat fat

18. FacilitatedDiffusion • Move from HIGH to LOWthrough 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

19. inside cell inside cell outside cell outside cell Simple vs. facilitated diffusion simple diffusion facilitated diffusion LOW lipid H2O protein channel H2O HIGH

20. 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 ATP Notice the direction of Amino Acid movement and the concentrations! Na+ activates the pump. Low High

21. Quick Review… simplediffusion facilitateddiffusion ATP activetransport

22. 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?

23. Movement of Water Across Cell Membrane Osmosis Osmosis and the Egg Demonstration

24. 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

25. Osmosis • diffusion of water from high concentration of WATER to low concentration of water • across a semi-permeable membrane High Low

26. Keeping water balance (Homeostasis) freshwater balanced saltwater • Cell survival depends on balancing water uptake & water loss

27. Keeping right amount of water in cell Hypotonic • 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

28. Controlling water • Contractile vacuole in Paramecium

29. Hypertonic • 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

30. Isotonic • 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

31. BLOOD! Animated Cell Responses to Solution Concentrations: http://www.phschool.com/science/biology_place/labbench/lab1/watpot.html

32. Learning through Osmosis?

33. 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!

34. Cells need ENERGY to power biochemical reactions.

35. How does a biochemical reaction work? Product Reactant Reactant Product Endo – inside Exo – outside Energy is absorbed or released by the reaction. Reactants ENTER the reaction. Product Product Product Products are PRODUCED by the reaction.

36. EXOthermic Reaction = RELEASES energy Product Reactant Reactant Product EXOTHERMIC Reactants ENTER the reaction. Energy is RELEASED by the reaction. Product Product Product Products are PRODUCED by the reaction.

37. ENDOthermic Reaction = ABSORBS energy Product Reactant Reactant Product Energy is ABSORBED by the reaction. Reactants ENTER the reaction. ENDOTHERMIC Product Product Product Products are PRODUCED by the reaction.

38. ENERGY TIME Exothermic Reaction = Releases Energy ACTIVATION ENERGY = energy required to cause the reaction to occur. Energy RELEASED

39. ENERGY TIME Endothermic Reaction = Absorbs Energy ACTIVATION ENERGY = energy required to cause the reaction to occur. Energy ABSORBED

40. Any Questions?