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Cell Membrane & Cellular Transport

Cell Membrane & Cellular Transport. Homeostasis – the maintenance of internal stable conditions. The cell membrane keeps the cell in balance. Membrane Functions. Provides a selectively permeable barrier around the cell. Controls the passage of substances in and out of the cell.

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Cell Membrane & Cellular Transport

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  1. Cell Membrane& Cellular Transport

  2. Homeostasis –the maintenance of internal stable conditions The cell membrane keeps the cell in balance.

  3. Membrane Functions • Provides a selectively permeablebarrier around the cell. • Controls the passage of substances in and out of the cell. • Maintains homeostasis for the cell.

  4. Membrane Structure • Phospholipid bilayer (nonpolar) • Membrane proteins: act as transport channels. • Carbohydrate chains: act as “ID” tags for the cell. • Cholesterol: provides stability for the membrane. http://library.thinkquest.org/C004535/media/cell_membrane.gif

  5. inside cell outside cell Phospholipid Bilayer • Phospholipids:phosphate head and lipid tail. • Phospholipid Bilayer:two layers. Hydrophilic = attracts water Phosphate Head Lipid Tails PhospholipidBilayer Hydrophobic = repels water

  6. The cell membrane is semipermeable,which means only some material can get in or out. So what needs to get across the membrane? Sugar Lipids Amino Acids O2 H2O Salt Waste

  7. How do you build a semi-permeable cell membrane? • Channels are made of proteins. • Proteins act as doors in the membrane. Protein Channelsin Bilipid Membrane Bilipid Membrane

  8. DiffusionMolecules move from HIGH to LOW concentration; this continues until equilibrium is reached. • Simple diffusion: directly through membrane. • Facilitated diffusion: help through a protein channel. NO energy needed!! HIGH LOW

  9. Active Transport • Cells use energy to move against concentration gradient - from LOW to HIGH. • Particles that are polar (charged) must move through a protein channel. • Use protein pump • requires energy (ATP) ATP

  10. Transport of Molecules • Endocytosis: takes material into cell by cell membrane making pockets. • Phagocytosis – “cell eating”; cell engulfs particles • Pinocytosis – cell takes in liquid from surrounding environment. • Exocytosis: process forcing contents out of the cell.

  11. Endocytosis PHAGOCYTOSIS PINOCYTOSIS

  12. Exocytosis

  13. Transport Summary simplediffusion (Smaller molecules) facilitateddiffusion ATP activetransport (Larger molecules)

  14. PASSIVE Does NOT require energy Goes with the concentration gradient (high to low) Simple Diffusion, Facilitated Diffusion ACTIVE Requires energy from ATP Goes against the concentration gradient (low to high) Active Transport, Endocytosis, Exocytosis Types of Cellular Transport

  15. Osmosismovement of water across cell membrane. HIGH H2O LOW H2O

  16. Effects of Osmosis on Cells (osmotic pressure) • Hypertonic: higher concentrations of solute; less H2O. • Isotonic: equal concentrations of solute. • Hypotonic: lower concentrations of solute; more H2O.

  17. http://www.glencoe.com/sites/common_assets/science/virtual_labs/LS03/LS03.htmlhttp://www.glencoe.com/sites/common_assets/science/virtual_labs/LS03/LS03.html

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