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DIFFUSION AND OSMOSIS

DIFFUSION AND OSMOSIS. CHAPTER 3 SECTION 4. Diffusion. The net movement of particles of a substance from an area of greater concentration to an area of lower concentration

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DIFFUSION AND OSMOSIS

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  1. DIFFUSION AND OSMOSIS CHAPTER 3 SECTION 4

  2. Diffusion • The net movement of particles of a substance from an area of greater concentration to an area of lower concentration • Passive Transport is the movement of molecules across a cell membrane without energy input from the cell A.K.A diffusion across a membrane

  3. Diffusion can occur across membranes (this is called passive transport) but membranes are not required for diffusion to take place. • Diffusion occurs down a concentration gradient, which is a difference in concentration of a substance from one area to another • Molecules move from high concentration to low until equilibrium is reached • Equilibrium is a “Balance” • When the molecules moving in one direction are equal to the # moving in the other direction.

  4. Osmosis • The passive transport of WATER through a semi-permeable membrane • If the solute cannot diffuse through the membrane to reach equilibrium, then the water moves instead

  5. Hypertonic – a solution w/ a higher concentration of solute Hypotonic– a solution w/ a lower concentration of solute Isotonic – a solution in which solute concentrations are equal. Equilibrium To avoid confusion: we will always ask questions about the solution that the cell is in. Ex. In the top picture, what type of solution is the cell in?

  6. When a cell is in a hypOtonic solution The solution has a lOw concentration Water rushes into the cell to dilute the high concentration of solute inside the cell The cell swells up like an O Remember: We can’t remove the solute from the cell because of the membrane, so water moves into the cell to dilute it. Think Kool-Aid: If your Kool-Aid is too strong, you can’t take any powder out of the pitcher, so you add more water to dilute it.

  7. When a cell is in a hypertonic solution The solution has a higher concentration Hyper kids are high energy Water rushes out of the cell to raise the concentration of solute inside the cell The cell shrivels up Remember: We can’t add more solute to the cell because of the membrane, so water moves out of the cell to raise the concentration Think Kool-Aid: If you can’t change the amount of mix in the pitcher, adding less water is the only way to make the Kool-Aid stronger

  8. When a cell is in an isotonic solution The solution has the same concentration as the cell Iso means the same This does not mean that nothing moves Equal amounts of water move into and out of the cell keeping the concentrations the same The cell and the solution are at an equilibrium

  9. SELECTIVE TRANSPORT • Large molecules do not pass as easily through the hydrophobic regions of the cell membrane. • Most get assistance from channel (carrier) proteins • 2 types • Facilitated diffusion • Active transport

  10. Facilitated Diffusion– the transport of substances through channels in either direction through the cell membrane • It is still a form of diffusion, which means it goes down the concentration gradient from high to low • It is still a form of passive transport, which means it takes NO energy from the cell

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