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Phospholipid Bilayer and Cell Transport: Structure and Function

This lesson explores the structure and function of the phospholipid bilayer in cell membranes, as well as the different types of passive and active transport mechanisms. Topics covered include diffusion, osmosis, facilitated diffusion, concentration gradients, and equilibrium.

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Phospholipid Bilayer and Cell Transport: Structure and Function

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  1. Bell Work: Draw a phospholipid bilayer (double layer of phospholipids) and arrange the tails on the inside

  2. Bell Work • Pick up: • Notes page on front table • Have out: • Cell membrane color sheet in your notebook • Homework Assignment Notice: • Membrane color sheet = due today • Edpuzzle Membrane Transport video = due by tonight at midnight • Edpuzzle Osmosis video = due by Thursday night at midnight

  3. Bell Work • Have out and be studying: • Your cell transport notes page AND your POGIL from yesterday • Quiz in just a few minutes

  4. Phenomena

  5. Membrane Structure and Cell Transport Chapter 5

  6. 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.

  7. Choose with your shoulder partner:

  8. Homeostasis • Define homeostasis: • Macro example: • Micro example: Maintaining a stable internal balance 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.

  9. Cell Membrane - Function • All cells have a cell membrane • Functions: • Controls what enters and exits the cell (to maintain the internal balance called homeostasis) • Provides protection and support for the cell

  10. Cell Membrane - Structure • Structure of cell membrane Lipid Bilayer -2 layers of phospholipids • Phosphate head is polar (water loving) • Fatty acid tails non-polar (water fearing) • Proteins embedded in membrane

  11. Semi – Permeable (Selectively Permeable) • allows certain molecules or substances to pass through it • Keeps other molecules out • The structure helps it be selective!

  12. Frogs Explain to your lizard what semi-permeable means

  13. 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? • Will starch pass through the membrane? How will we know?

  14. Cell Transport Controlled via the Cell Membrane Passive Transport Active Transport Does NOT require energy, moves from HIGH concentrations to LOW concentrations DOES require energy, moves from LOW concentrations to HIGH concentrations, moves LARGE molecules (glucose) via transport proteins Diffusion Osmosis Facilitated Diffusion Moves small molecules, like CO2 & O2 gases, directly through the membrane Protein Pumps Movement of water across the membrane Endocytosis Exocytosis Uses transport proteins to move large molecules through the membrane WITHOUT energy Materials EXIT the cell through a vesicle formed by the Golgi Body Materials ENTER the cell through a vesicle formed by the membrane 3 Types of Solutions Transport proteins that require energy to do work. Example: Sodium / Potassium Pumps are important in nerve responses. Hypertonic Isotonic Hypotonic Water moves out of the cell & it shrinks Water moves equally in and out of the cell; it stays the same size Water moves into the cell & it swells

  15. Weeee!!! high low This will be hard work!! high low Cell Membrane Transport • Two main types of cell transport: • Passive: • Active: the movement of substances across the cell membrane without energy. the movement of substances across the cell membrane with the use of energy.

  16. Lizards: Explain to your frogs the difference between passive and active transport

  17. Types of Passive Transport(No energy) (High to Low) • Diffusion • Osmosis • Facilitated Diffusion Movement of SOLUTES (small molecules) Movement of WATER molecules Diffusion of large or polar molecules using protein channels or pores

  18. Concentration Concentration: Two parts needed to determine concentration: • Solvent: • Solute: The amount of a substance in a given volume • The substance with the greatest volume • What the solute is dissolved in. • The substance with the smaller volume • The substance(s) that are dissolved in the solvent.

  19. Solute vs Solvent Example: Salt water • Solvent? • Solute? Water Salt

  20. Solute and Solvent Example: Food coloring in water

  21. Concentration Gradient

  22. 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.

  23. Passive Transport Leads to Equilibrium • Equilibrium: When the concentration of molecules is the same throughout the space the molecules occupy.

  24. Frogs: Explain why molecules want to move from areas of high concentration to low

  25. How does this affect cells? Lungs: can send CO2 out of the red blood cells and get O2 in Cells: can get O2 into them and send out CO2 • Diffusion: • Osmosis: • Remember: All passive transport moves from high to low concentration trying to create an equilibrium 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

  26. Facilitated Diffusion (Passive) • Diffusion of molecules unable to get across membrane by going through the phospholipid layer • Require use of carrier protein channels • Examples: Glucose (too large), Na+ (has a charge) • Definition: • Video - "Facilitated Diffusion”

  27. Facilitated Diffusion (Passive) • Some molecules are too big to enter the cell without help

  28. Demonstration Check: Record the results of the corn starch in iodine experiment. Did iodine enter the cell? How do you know? Did starch exit the cell? How do you know?

  29. Passive Transport Review: Three types: • Diffusion: • Osmosis: • Facilitated diffusion: Common Characteristics: • Don't use any energy • Move from high to low concentration small solutes (O2 or CO2) moving across the membrane movement of water across the membrane larger solutes (glucose) moving across the membrane through channels or pores

  30. Lizards: Summarize the 3 types of passive transport to your frog

  31. Exit Ticket • Differentiate between diffusion and facilitated diffusion?

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