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Ch. 3 Part 2

Ch. 3 Part 2. Cell Transport. Movement Across Cell Membranes. Cell membranes are a barrier, but substances must be able to get in and out 5 main methods of transport Simple diffusion Osmosis Facilitated diffusion Active transport Vesicles. Simple Diffusion.

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Ch. 3 Part 2

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  1. Ch. 3 Part 2 Cell Transport

  2. Movement Across Cell Membranes • Cell membranes are a barrier, but substances must be able to get in and out • 5 main methods of transport • Simple diffusion • Osmosis • Facilitated diffusion • Active transport • Vesicles

  3. Simple Diffusion • Molecules move from an area of high concentration to an area of low concentration (H → L) • Through cells – only lipid-soluble molecules (steroids) or very small molecules (O2, H2O, CO2) can do this • Only stop when equilibrium is reached

  4. Simple Diffusion

  5. Osmosis • Diffusion of water • Water is always looking to keep a balance between inside and outside the cell • 3 types of solutions result in osmosis • Hypotonic • Hypertonic • Isotonic

  6. Osmosis • Hypotonic • Concentration of solute is higher outside the cell than inside the cell • Water moves inward to balance • Cell size increases – animal cells can burst (lysis) • Hypertonic • Concentration of solute is lower outside the cell than inside the cell • Water moves outward to balance • Cell size decreases – shrivel up (crenation) • Isotonic • Concentration of solute is equal inside and outside • Water moves, but the balance remains • Cell size does not change

  7. *Osmosis and Blood Cells • Blood cells have a salinity of 0.9%. • If they are in a salinity greater than that, what will happen? • If they are in a salinity less than that, what will happen? • If they are in a salinity equal to that, what will happen?

  8. Osmosis

  9. Facilitated Diffusion • Same as diffusion with help (facilitated) • This help is done by proteins • 2 types of proteins • Channel proteins • Form a pore or channel where ions can pass through • Many channels are gated and can be closed • Carrier proteins • Has a binding site for a specific molecule • Can move substances in and out

  10. Facilitated Diffusion

  11. Active Transport • Forces molecules to go from one side to the other, against concentrations • Must be performed with proteins • Must have energy to occur • Example: • Sodium-potassium pump

  12. Active Transport • Sodium-potassium pump • Essential for neural impulses to be sent • Pumps 3 sodium out of the cell • Pumps 2 potassium into the cell • This helps maintain the correct gradient of ions

  13. Vesicles • Exocytosis • Removes large molecules out of the cell by using vesicles (pouches) • Endocytosis • Brings large molecules into the cell using vesicles • Pinocytosis – cell drinking • Phagocytosis – cell eating

  14. Vesicles

  15. Transport Summary • Active transport • Moves materials from low to high • Goes against the concentration gradient • Energy required • Passive transport • Moves materials from high to low • Goes with the concentration gradient • No energy required

  16. Which is which? • Which types of transport are passive or active? • Which types of transport use proteins? • Simple diffusion? • Osmosis? • Facilitated diffusion? • Active transport? • Vesicles?

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