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Transcript
Cellular Transport Notes Ch. 7.2 Plasma Membrane (p.175-178) Ch. 8.1 Cellular Transport (p.195-200) Cell Membranes ALL cells have a Cell Membrane 2. Functions: a. Controls what enters and exits the cell to maintain an internal balance called homeostasis b. Provides protection and support for the cell 1. TEM picture of a real cell membrane. Cell Membranes (continued) 3. Structure of cell membrane Lipid Bilayer -2 layers of phospholipids Phosphate head is polar (water loving) b. Fatty acid tails non-polar (water fearing) c. Proteins embedded in membrane a. Phospholipid Lipid Bilayer Polar heads Fluid Mosaic love water Model of the & dissolve. cell membrane Non-polar tails hide from water. Carbohydrate cell markers Proteins Membrane movement animation Cell Membranes (continued) 4. Cell membranes have pores (holes) in it which makes it Selectively Permeable: Allows some molecules in and keeps other molecules out (the structure helps it be selective!!) Pores Structure of the Cell Membrane Outside of cell Proteins Lipid Bilayer Transport Protein Animations of membrane Go to structure Section: Carbohydrate chains Phospholipids Inside of cell (cytoplasm) Cell Membrane “Use Textbook” ANSWER THE FOLLOWING: 1. What is the function of the cell membrane? (p. 175) 2. Describe the structure of the cell membrane? (p. 176) 3. How many layers of lipids are there in the plasma membrane? (p. 177) 4. What are the proteins called that are found within the plasma membrane? (p.177) 5.Why is the structure of the cell membrane referred to as a “mosaic?”? (p.178) Cell Concentrations Cells are surrounded and filled with a liquid environment The cytoplasm contains a solution of different substances. Cell Concentrations A solution is a mixture of two or more substances. Solute – dissolved substance (salt/sugar) Solvent – dissolves solute (water) Cell Concentrations Substances will move across the cell membrane if their concentrations are unequal. Isotonic Solution Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium) A cell in an isotonic solution Water moves in and out at the same rate 10% Solute How much solvent inside? 90% solvent Cell remains the same! 10% Solute How much solvent outside? 90% solvent Hypotonic Solution Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)! A cell in a hypotonic solution Water moves in 20% Solute How much solvent inside? 80% solvent Cell swells! 10% Solute How much solvent outside? 90% solvent Hypertonic Solution Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)! A cell in an hypertonic solution Water moves out 10% Solute How much solvent inside? 90% solvent Cell shrinks! 20% Solute How much solvent outside? 80% solvent What type of solution are these cells in? A B C Hypertonic Isotonic Hypotonic Types of Cellular Transport 2. 3. Weeee!! ! Passive Transport cell doesn’t use energy 1. Diffusion Facilitated Diffusion Osmosis •Animations of Active Transport & Passive Transport high low Active Transport cell does use energy 1. 2. 3. Protein Pumps Endocytosis Exocytosis This is gonna be hard work!! high low Passive Transport cell uses no energy molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration. (HighLow) 3 Types of Passive Transport 1. 2. 3. Diffusion- diffusion of particles Facilitative Diffusion – diffusion with the help of transport proteins Osmosis – diffusion of water Passive Transport: 1. Diffusion 1. Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) • Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out. Simple Diffusion Animation Passive Transport: 2. Facilitated Diffusion A 2. Facilitated diffusion: diffusion of specific particles with HELP from a transport proteins a. Transport Proteins are specific – they “select” only certain molecules to cross the membrane b. Transports larger or charged molecules (sugar) Facilitated diffusion (Channel Protein) Carrier Protein B Diffusion (Lipid Bilayer) Passive Transport: 2. Facilitated Diffusion Glucose molecules Cellular Transport From aHigh Concentration High Cell Membrane Low Concentration Through a Go to Section: Transport Protein Protein channel Low Channel Proteins animations Passive Transport: 3. Osmosis Osmosis animation 3.Osmosis: diffusion of water through a selectively permeable membrane Water moves from high to low concentrations •Water moves freely through pores. •Solute (green) to large to move across. How Organisms Deal with Osmotic Pressure Paramecium (protist) removing excess water video •Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. •A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding. •Salt water fish pump salt out of their specialized gills so they do not dehydrate. •Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water. Active Transport •cell uses energy (ATP) •actively moves molecules to where they are needed •Movement from an area of low concentration to an area of high concentration (Low High) 3 Types of Active Transport 1. 2. 3. Protein Pumps- transport macromolecules across the cell membrane Endocytosis- material ENTERING the cell Exocytosis- material EXITING the cell Types of Active Transport 1. Protein Pumps transport proteins that require energy to do work •Example: Sodium / Potassium Pumps are important in nerve responses. Sodium Potassium Pumps (Active Transport using proteins) Protein changes shape to move molecules: this requires energy! Types of Active Transport 2. Endocytosis: taking bulky material into a cell • Uses energy • Cell membrane in-folds around food particle Aka: “cell eating” • forms food vacuole & digests food (This is how white blood cells eat bacteria!) 2 Types of Endocytosis… 1) Phagocytosis: large PARTICLES are engulfed 2) Pinocytosis: WATER drops are engulfed Types of Active Transport 3. Exocytosis: Forces material out of cell in bulk • membrane surrounding the material fuses with cell membrane Cell changes shape – requires energy EX: Hormones or wastes released from cell • Endocytosis & Exocytosis animations Compare: Passive to Active Transport Passive Transport -Moves from HIGH to LOW 3 Types: 1) Diffusion- particles move fm H to L 2) Osmosis- water moves fm H to L 3) Facilitated Diffusionparticles move fm H to L with the HELP of transport protein REQUIRES NO ENERGY (ATP) Active Transport Moves from LOW to HIGH 3 Types: 1) Endocytosis- particles into the cell 2) Exocytosis- particles exists the cell 3) Protein Pump- particles moves with HELP of a transport protein with ATP REQUIRES ENERGY (ATP)