1.Cell BoundariesChapter 6

2. What are boundaries? We have borderssurroundingcountries We have boundarieson a playing field Why are bordersimportant? 3. What are the borders of acell? Cell membrane Thin, flexible barrier Cell wall Plant, algae, fungi, prokaryotes Strong supporting layer 4. Cell Membrane What does it do for cell? Controls what goes in and out Regulates molecules moving from one liquid side of thecell to the other liquid side of the cell Protects Supports 5. Cell Membrane Lipid bilayer What are lipids? What does bi- mean? Whats a layer? A cell membrane is made of two layers of lipid molecules 6. Cell membrane Phospholipids bilayer Made of a negatively chargedphosphate head PO43- Attracts water because the phosphate is charged (-) Water is a polar , slightly positive ends and slightly negative ends Attached to the phosphategroup are 2 fatty acid chains Hydrophobic= dont like water So the inside of the cell membrane doesnt let water in but the outside allows cells to be dissolved in aqueous environments 7. Other things in themembrane Proteins embedded in lipid bilayer Carbohydrates attached to proteins So many different molecules in membrane, we call it a mosaic of different molecules 8. Proteins Proteins help things get across membrane Kinda like a pump 9. Carbohydrates Chemical identification cards ID card of cell Helps individual cells id each other 10. Cell Walls Outside cell membrane(does NOT replacemembrane!!!) Plants, algae, fungi,prokaryotes Have pores to allowthings in Function: SUPPORTand PROTECT 11. Cell walls made of Protein and carbs Plant cell walls made up of CELLULOSE This is a tough carbohydrate Wood and paper 12. The Cell Membrane A biological membrane Cells exist in liquid environments Things need to get in and out of cell Different ways to do this. 13. Concentration (conc.) Solution Mix of 2 or more substances Solutes Substance dissolved in solution Concentration Molarity (M) is # of Moles of a substance per liter of solution 6.02 x 1023 small things (molecules, atoms, ions, electrons, ions, etc) Moles is a unit for measuring EXTREMELY small things is mass of SOLUTE in a given volume of solution (g/L) What is the concentration of 12 grams of salt dissolved in 3liters of water? 12g/3L= 4g/L 14. Diffusion Particles constantly move Collide randomly Spread out randomly Diffusion is moving from area of HIGH conc. toarea of LOW conc. This is what we call the CONCENTRATIONGRADIENT 15. Equilibrium When the conc. Of a system is the same throughout (same conc. on both sides) 16. What happens when wereach equilibrium? Particles continue moving across membrane but inboth directions!***No more changes in concentration 17. If things can cross amembrane we call themembrane PERMEABLEIf things canNOT cross amembrane we call themembrane IMPERMEABLE 18. Biological membranesare SEMI-PERMEABLE A.K.A. Selectively permeable Cell membranes are picky 19. Whats this have to dowith cells? Cell have liquid inside and are found in liquid environment We have substances (solutes) inside and outside cell Unequal concentrations means we get DIFFUSION!!! B/c diffusion depends on random particle movements, substances diffuse across membranes without requiring the cell to use energy 20. What diffuses across themembrane??? Small, uncharged(non-polar) molecules Examples: Carbon dioxide Oxygen 21. Cells are always trying to Maintain Equilibrium by3 ways PASSIVE Transport ACTIVE Transport 2 types 1 type Requires NO energy REQUIRES Energy Goes with Conc. Gradient Goes Against Conc. Gradient types: ACTIVE TRANSPORT SIMPLE DIFFUSION- Involves transporter No protein required membrane protein and Small, uncharged particlesENERGY (ATP) FACILITATED DIFFUSION- CHANNEL or CARRIER proteins Trans-membrane protein channel Protein with a specific shape; open-close mechanism Ex. Osmosis and ligand-gated channels 22. Osmosis Water (H2O) can pass easily through mostbiological membranes Def: Diffusion of Water through a semi-permeablemembrane Small molecules of water can sometimes diffuseacross easily (no protein needed) AQUAPORIN: What does aqua mean??? Protein in cell membrane that allows water through (speeds updiffusion of water across the membrane) Type of Facilitated diffusion (more on this later) 23. How Osmosis works We have water molecules and some other molecules, letssay sugar If we have more water on one side of the membrane (HIGHconc. of H2O), then the water will diffuse across Membrane will let water thru but not sugar Water can move back and forth (not sugar) 24. Water moves from areas of HIGH conc. To areas of LOW conc. Water moves across till equilibrium is reached Isotonic: when conc. Of both solutions is equal Hypertonic: above strength When we begin with more sugar in water More concentrated sugar solution on side A Hypotonic: below strength When we end with less sugar Dilute sugar solution on side A 25. Osmotic Pressure Central vacuole fills with water and exerts andout ward pressure on cell membrane and cellwall Cell wall does NOT allow cell to expand past acertain sizeOsmoregulation Osmoregulation means by which cells keep the concentration of cell cytoplasm or blood at a suitable concentration. 26. Problems in Plant Cell 27. Osmotic Pressure Pressure exerted by osmosis on theHYPERTONIC side of a semi-permeablemembrane Think about blowing up a balloon Can cause serious problems for cell Cell is full of sugar, salts, proteins, molecules Inside of cell is Hypertonic Osmotic pressure should make fresh water go? In or Out? In Cell will become inflated/swollen Too much cell will burst like a balloon 28. Why dont all our cells burst? What are our cells (animal) contained in? Fresh water? No..blood or other fluids, which are ISOTONIC The conc. Of sugars, salts, proteins and molecules in these fluids is the same as the conc. in the cell Bacteria and plant cells They DO come in contact with fresh waterwhat dothey have PROTECTING them? CELL WALL Prevent cells from expanding even when theres a lot of osmotic pressure But, cell walls are prone to injuries when there is too much osmotic pressure 29. Which is a RBC in isotonic solution? RBC in hypertonic solution? RBC in hypotonic solution? 30. How do big moleculesdiffuse across a membraneso quickly if the membraneis selectively permeable? 31. Problems for diffusion Things too large (like Glucose!) Charged molecules and Polar molecules Positive/negative Opposites attract but likes do not These all present serious problems for thingsgetting across membranes 32. Facilitated Diffusion What does facilitate mean? Proteins are the extra help escorts across the membrane We call these membrane proteins Protein channels Carrier proteins LIGAND receptor proteins 33. Facilitated Diffusiontakes place through proteins, or assemblies of proteins, embedded inthe plasma membraneProtein channelsCarrier proteinsLIGAND receptor proteins 34. Facilitated Diffusion(continued) FAST SPECIFIC Still diffusionso we only seeit from highconcentrationto low Does NOTrequire energy 35. What about when we want togo against theconcentration?(From low concentration tohigh?) 36. What do we need??? ENERGY!!!! 37. ACTIVE transport Process that moves molecules against the concentration gradient Requires ENERGY A protein pumps small molecules and ions across a cell membrane againstthe conc. Gradient Direct and Indirect Active transport (see animation) Forms of molecular transport proteins are used to pump small moleculesand ions across membrane even against the conc. grad. Direct: every 3 Na+ ions pumped across for every 2 K+ ions Indirect: Build up of ions on one side opens up another channel to shuttle in other molecules (Na+/Glucose channel) Electrochemical gradient membrane potential (cell membrane is negative) Na+ opens build up on the outside of the celldraws water out of the cell so it doesnt swell or burst! To pump large molecules and clumps 2 other processes: Exocytosis: exo-means.cyto- means..-sis means. Endocytosis: endo-means.cyto- means..-sis means. They can change shape of membrane 38. Build up of Na+ ions on one side of membrane from Na+/K+ pumpNow Na+ will flow thru another channel that allows one glucose intoo!Pretty convenient! 39. Endocytosis When cells need to take in large material Process of taking material into the cell by process of infolding, or pockets, of the cell membrane Pocket breaks loose from cell membrane and forms a vacuole or vesicle inside the cell Two Types Phagocytosis Pinocytosis 40. Two types of endocytosis:1. Phagocytosis cell eating Extensions of cytoplasm surround the particleand package it within a food vesicle Cell then engulfs the package Amoebas2. Pinocytosis cell drinking When cell needs to take up liquid Tiny pockets in cell membrane form Fill with liquid or many smaller molecules Then pinch off to form vesicles inside of cell 41. Exocytosis Exo- means Cyto means Sis means When cell releases large amounts of material Excretes stuff Membrane of vacuole surrounding particle inside cell fuses with the cell membrane The contents in vacuole are then forced out of the cell We see this in removal of water by contractile vacuoles 42. Cells are always trying to Maintain Equilibrium by3 ways PASSIVE Transport ACTIVE Transport 2 types 1 type Requires NO energy REQUIRES Energy Goes with Conc. Gradient Goes Against Conc. Gradient types: ACTIVE TRANSPORT SIMPLE DIFFUSION- Involves transporter No protein required membrane protein and Small, uncharged particlesENERGY (ATP) FACILITATED DIFFUSION- CHANNEL or CARRIER proteins Trans-membrane protein channel Protein with a specific shape; open-close mechanism Ex. Osmosis and ligand-gated channels 43. MEMBRANE MAMBO!!! 44. Membrane Mambo 10 minutes to plan 2 teams/Cells Nucleus for each team Each member must be assigned a molecular role (must be labeled) Membrane protein(s) Molecule A (ex. Glucose) Molecule B (ex. Na+) Molecule C (ex. Water) Remember molecules are ALWAYS moving!!! MUST act out the following types of membrane transport: Simple Diffusion Osmosis Facilitated diffusion (channel, carrier and ligand) Active transport (direct and indirect) Be prepared to determine the concentration on either side of the membrane Your Nucleus must turn in a paper with every ones name and roles Summary of how each scenario will be acted out