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Understanding Cell Boundaries: Importance of Walls and Membranes

Explore the significance of walls and membranes in cells, emphasizing selective permeability, passive and active transport, osmosis, and types of endocytosis and diffusion. Understand how cells regulate the movement of substances in and out for maintaining homeostasis.

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Understanding Cell Boundaries: Importance of Walls and Membranes

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  1. Cell Boundaries

  2. Why do houses need walls? Protect it from the environment Decide what can come in and go out

  3. >> Check for Understanding • How does a window screen show selective permeability?

  4. >> Check for Understanding • What are some things that can pass through a window screen? • What are some things that cannot? • Why is it important for a cell membrane to regulate what moves into and out of a cell?

  5. Cell Borders (solute- substance dissolved in solvent) • Cell Membrane – controls/regulates what enters and leaves the cell. (***semi-permeable***) • Phospholipid bilayer– 2 layers of phospholipids with a “mosaic” of proteinsand carbs. (In ALL cells!) • maintainsHomeostasis

  6. Cell Borders • Cell Wall– Provides support, shape, and protection. Rigid, NOT flexible (In plants!) • Made of cellulose – a tough carbohydrate

  7. General Terms Concentration Gradient – The unequal distribution of particles Homeostasis HIGH LOW

  8. 2 Ways to Cross the Membrane • Passive Transport– NO energy is required to move a substance across the membrane • (***** moves along gradient/high to low) • Active Transport– EnergyISREQUIRED to move a substance across the membrane • (**** moves against gradient/low to high)

  9. High Concentration Passive Transport Low Concentration

  10. Passive Transport Diffusion

  11. Passive Transport Diffusion

  12. High Concentration Active Transport Low Concentration

  13. Active Transport

  14. Active Transport

  15. Passive Transport - Diffusion • Diffusion - movement of particles/solutefrom areas of highconcentration of solute to areas of low concentration of solute. • What is concentration? What is a solute? • When the concentration is the same throughout, equilibrium is reached. • Temperature and size of molecule affect the rate of diffusion.

  16. Passive Transport - Osmosis • Osmosis – movement of waterparticles across a membrane by diffusion. • *****Water moves from low soluteto high solute. http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf • http://www.youtube.com/watch?v=sdiJtDRJQEc&NR=1&safety_mode=true&persist_safety_mode=1 • solute = thing being dissolved. Ex - salt • NO ENERGY Required.

  17. How Osmosis Works in the Cell • Isotonic Solution – Concentration of solutes outside and inside cell are equal. • Equilibrium (cell stays the same)

  18. How Osmosis Works in the Cell • Hypertonic solution - Concentration of solutes outside is higherthan inside the cell. • Water out (Cell shrinks)

  19. How Osmosis Works in the Cell • Hypotonic solution - Concentration of solutes outside is lower than it is inside the cell. • Water in (Cell swells)

  20. Red onion and salt water. • http://www.youtube.com/watch?v=nHWUAdkYq4Q&feature=related&safety_mode=true&persist_safety_mode=1 • http://www.youtube.com/watch?v=lzDlGl3b4is&NR=1&safety_mode=true&persist_safety_mode=1

  21. Solutes Outside the cell

  22. Solutes Outside the cell

  23. Solutes Outside the cell

  24. Asd

  25. Passive Transport:Facilitated Diffusion • Facilitated Diffusion– Large molecules (like glucose) move across the membrane with the helpof protein channels. • Since it is Facilitated Diffusion, does it require energy?? • http://www.stolaf.edu/people/giannini/flashanimat/transport/channel.swf

  26. Active Transport • Larger molecules (sugar) and ions (Na+, K+, Ca+2) pass across the membrane using proteins and requiring ENERGY. • Substances move from low to high concentrations.

  27. Active Transport: Exocytosis and Endocytosis • Exocytosis- Wastes and products are packaged in vesicle by the Golgi and sent OUT of cell • http://www.coolschool.ca/lor/BI12/unit4/U04L05/exocytosis.html

  28. Endocytosis– cell membrane forms vesicle and brings things INTO the cell. • http://www.coolschool.ca/lor/BI12/unit4/U04L05/endocytosis_final.html

  29. Types of Endocytosis • Phagocytosis – engulfs by surrounding membrane around solids. • “Phago-” means “to eat” • http://cdn.pbh2.com/wordpress/wp-content/uploads/2012/07/white-blood-cell-attacks-bacteria.gif • http://www.youtube.com/watch?v=aWItglvTiLc&feature=related • Pinocytosis – pinches membrane and brings in liquids. • “Pino-” drink “to pinch”

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