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Bell Work: Draw a phospholipid bilayer (double layer of phospholipids) and arrange the tails on the inside Membrane Structure and Cell Transport Chapter 5 Objectives: CLE 3210.1.5 - Compare different models to explain the movement of materials into and out of the cell. SPI 3210.1.8 - Compare active and passive transport. RLE 2010.2.1 - Recognize the importance of homeostasis as a survival mechanism. Choose with your shoulder partner: Homeostasis • Define homeostasis: A tendency toward a state of equilibrium • Macro example: • Micro example: We maintain a stable body temperature. Cells use the cell membrane to regulate what comes in and out of the cell to keep steady levels of nutrients, water and other substances. Cell Membrane - Function 1.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 Cell Membrane - Structure 3.Structure of cell membrane Lipid Bilayer -2 layers of phospholipids a.Phosphate head is polar (water loving) b.Fatty acid tails non-polar (water fearing) c.Proteins embedded in membrane Semi – Permeable (Selectively Permeable) •allows certain molecules or substances to pass through it •Keeps other molecules out •The structure helps it be selective! Frogs Explain to your lizard what semipermeable means Demonstration • Cornstarch • Plastic bag (represents a cell with a semi-permeable membrane) • Beaker w/ water and Lugols Iodine Prediction: • Will Iodine be allowed to pass through the membrane? • How will we know? Controlled via the Cell Membrane Passive Transport Active Transport Does NOT require energy, moves from HIGH concentrations to LOW concentrations Diffusion Moves small molecules, like CO2 & O2 gases, directly through the membrane Hypertonic Water moves out of the cell & it shrinks Osmosis Movement of water across the membrane 3 Types of Solutions Isotonic Water moves equally in and out of the cell; it stays the same size Facilitated Diffusion Uses transport proteins to move large molecules through the membrane WITHOUT energy Hypotonic Water moves into the cell & it swells DOES require energy, moves from LOW concentrations to HIGH concentrations, moves LARGE molecules (glucose) via transport proteins Protein Pumps Transport proteins that require energy to do work. Example: Sodium / Potassium Pumps are important in nerve responses. Endocytosis Materials ENTER the cell through a vesicle formed by the membrane Exocytosis Materials EXIT the cell through a vesicle formed by the Golgi Body Cell Membrane Transport • Two main types of cell transport: o Passive: the movement of substances across the cell membrane without energy. o Weeee!! ! high low Active: the movement of substances across the cell membrane with the use of energy. This will be hard work!! high low Lizards: Explain to your frogs the difference between passive and active transport Types of Passive Transport (No energy) (High to Low) • Diffusion Movement of SOLUTES from high concentration to low concentration. • • Osmosis Movement of WATER molecules from an area of high water concentration to an area of lower water concentration. Facilitated Diffusion Diffusion of molecules across a membrane using protein channels or pores Concentration Concentration: The amount of a substance in a given volume Two parts needed to determine concentration: Solvent: • • • The substance with the greatest volume • What the solute is dissolved in. Solute: • The substance with the smaller volume • The substance(s) that are dissolved in the solvent. Solute vs Solvent Example: Salt water Solvent? Water Solute? Salt • • Solute and Solvent Example: Food coloring in water Concentration Gradient Passive Transport = High to Low Why will things move from high concentration to low concentration? All molecules are moving. As they bump into each other they move faster until there is even space between them. Passive Transport Leads to Equilibrium Equilibrium: When the concentration of molecules is the same throughout the space the molecules occupy. Frogs: Explain why molecules want to move from areas of high concentration to low How does this affect cells? Diffusion: Lungs: can send CO2 out of the red blood cells and get O2 in Cells: can get O2 into them and send out CO2 Osmosis: When cells need more water to perform hydrolysis, can pull water in from the blood. If cells need to remove water that built up after many sets of c tondensation, they can send water out to blood • Remember: All passive transport moves from high to low concentration trying to create an equilibrium Facilitated Diffusion (Passive) Definition: • Diffusion with the help of carrier protein channels • Usually for large molecules – like Glucose Video - "Facilitated Diffusion” Facilitated Diffusion (Passive) •Some molecules are too big to enter the cell without help Demonstration Check: Record the results of the corn starch in iodine experiment. Passive Transport Review: Three types: small solutes (O2 or CO2) moving across the Diffusion: membrane Osmosis: movement of water across the membrane Facilitated diffusion: larger solutes (glucose) • • • moving across the membrane through channels or pores Common Characteristics: Don't use any energy Move from high to low concentration • • Lizards: Summarize the 3 types of passive transport to your frog Exit Ticket •Differentiate between diffusion and facilitated diffusion?