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Cellular Transport

Explore how the plasma membrane structure, fluid mosaic model, membrane proteins, and types of transport mechanisms function to maintain homeostasis and allow movement of materials within cells. Learn about passive transport, facilitated diffusion, osmosis, active transport, endocytosis, and exocytosis.

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Cellular Transport

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  1. Cellular Transport Movement of Materials In and Out of a Cell

  2. Plasma Membrane • Maintains homeostasis (stable environment) • Membrane is “selectively permeable” • Only certain things can pass in and out

  3. Structure of the Plasma Membrane Fluid Mosaic Model Membrane is not rigid Molecules can move back and forth (fluid)

  4. Phospholipid Bi-layer • 2 layers of Phospholipids • Hydrophobic tails and hydrophilic heads

  5. Cholesterol molecules: sometimes found embedded in membrane to give it more strength and rigidity. Carbohydrate Chains: help cells identify each other

  6. Membrane Proteins • Protein Channels • Provide pathway for movement of certain materials • Anchor Proteins • Anchor molecules in membrane so they don’t move around • Enzyme Proteins • Take part in chemical reactions

  7. Receptor Proteins • Act as binding sites for specific molecules • Cellular communication • Recognize foreign cells • Tell cell to begin or stop activity

  8. Movement in a Liquid Medium • Cytoplasm has many different things dissolved in it. • Solvent = water • Solute = stuff dissolved (ex: sugar, salt) • Solution = the mixture of solvent and solute • Concentration = how much is dissolved

  9. All molecules are in constant random motion, so over time they will move from one location to another.

  10. Types of Transport

  11. Passive TransportDoesn’t require energy • Diffusion: • Movement of materials through the cell membrane. • Higher concentration to lower concentration • Does not require energy (ATP) • Ex:oxygen, carbon dioxide, water

  12. Dynamic Equilibrium: a point of balance that is reached when concentrations stop changing (but particles still moving!)

  13. Example of Diffusion Higher Concentration Outside Particles Diffuse Into Cell Equilibrium Reached (Diffuse In & Out Equally)

  14. Facilitated Diffusion: • Protein channels facilitate (help) movement of charged ions and large molecules like glucose to cross cell membrane • Energy (ATP) not needed

  15. Osmosis: • Movement (diffusion) of WATER through the cell membrane • From high concentration to low (of water) • No energy needed

  16. Aquaporins: • Water channel proteins • Involved in osmosis • Allow water to move easily through membrane by diffusion • Type of facilitated diffusion Oil (fat) and water don’t mix Channel helps water get through fatty membrane!!!

  17. Water moves into an area that is more concentrated with solute particles!!!! • Equilibrium is reached and concentrations are equal on both sides of membrane

  18. Osmosis Water moves to area where water is less concentrated

  19. Osmotic Pressure: force caused by net movement of water into or out of cell

  20. Isotonic Solution: of the same “strength” • Same concentration as cell • Hypertonic Solution: “above strength” • More concentrated than cell • Hypotonic Solution: “below strength” • Less concentrated than cell

  21. What will Happen? • To a cell in a: • Isotonic Solution? • Hypertonic Solution? • Hypotonic Solution? • Which way will water move? • Will it fill up and burst, shrink, or stay the same? • Types of Solutions: http://youtu.be/7-QJ-UUX0iY • Egg Experiment: http://youtu.be/SSS3EtKAzYc

  22. Plasmolysis: when a plant cell loses water • Normal plant cell – large vacuole stores water • In salt water, or in times of drought – water leaves cell to go into surroundings (wilts)

  23. Active Transport: • Requires energy (ATP) • Materials are moved from low to high concentration

  24. Protein Pumps: • Membrane proteins • Move small molecules and ions across membrane • Against concentration gradient (low to high) • Requires energy (ATP)

  25. Endocytosis • Folding in the membrane to form a vacuole • Take in large molecules, clumps of food or whole cells • Requires energy

  26. Types of Endocytosis • Phagocytosis • Cell “eating” • Cell engulf large particles by sending out extensions of cytoplasm • Ex: • Amoeba sends out pseudopods, • White blood cells eat bacteria and damaged cells

  27. Pinocytosis • Cell “drinking” • Cell takes in liquid • “Pinching in” of cell membrane to create a storage vacuole

  28. Exocytosis • Cells releasing (excreting) materials • Membrane of vacuole fuses with cell membrane

  29. Inner Life of the Cell • http://youtu.be/yKW4F0Nu-UY

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