Cell Processes

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Cell Processes

• S. Burnham
• HHS
• Biology

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How do smells get out of the balloon?

• Diffusion
• Selectively permeable membrane
• Homeostasis
• Active transport
• Hypertonic/hypotonic/isotonic
• Osmosis

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Concentration

• The mass of a solute in a given volume of
  solution
• If you dissolve 12 grams of salt in 3 liters of
  water, what is the concentration of salt in the
  solution?

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• 12g/3L 4g/L

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• Suppose you add 12 more grams of salt in to the
  solution. What would be the resulting
  concentration?

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• 12g 12g 24 g
• 24g/3L 8g/L

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• What if you then added another 3 liters of water
  to that solution. What would be the resulting
  concentration?

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• 3L 3L 6L
• 24g/6L 4g/L

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4g/L 8g/L 4g/L

• Which solution would be called the most
  concentrated?

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• 8g/L
• Why?
• 8g in 1L is more than 4g in 1L

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Diffusion

• Movement of particles from an area of high
  concentration to an area of low concentration
• Particles try to reach equilibrium
• Equilibrium is reached when the concentration of
  the solute is the same throughout the system

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Diffusion

• Substances diffuse across membranes without
  requiring the cell to use energy
• Particles of a solution continue to move across
  the membrane even when equilibrium is reached,
  there is just no further change in concentration

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Selectively Permeable

• A membrane through which some substances can pass
  through, but some cannot

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Hypertonic

• Solution has higher solute concentration than the
  cell
• Water will move from inside the cell to outside
  the cell
• Figure 7-16

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Hypotonic

• Solution has a lower solute concentration than
  the cell
• Water moves into the cell

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Isotonic

• Concentration of solutes is the same in and out
  of the cell

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Utilize Fig. 7-16

• A homeowner contracts a lawn company to add
  fertilizer to the lawn in order to make the grass
  grow better. This process is normally done by
  spraying a mixture of fertilizer and water onto
  the lawn
• What would happen if too much fertilizer and too
  little water were sprayed onto the lawn?

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• Can you suggest what happened to the cells of the
  grass?

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• In that case, was the fertilizer-water mixture
  hypotonic or hypertonic compared to the grass
  cells?

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Active Transport (Fig. 7-19)

• Movement of materials against the concentration
  gradient
• Requires energy
• Generally carried out by transport proteins in
  cell membrane
• Can be used to transport calcium, potassium, and
  sodium ions across the membrane

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Endocytosis

• Membrane infolds to take in materials
• Pocket breaks loose to form vacuole in the
  cytoplasm
• Phagocytosis taking in food amoeba's use this
  to take in food
• Pinocytosis membranes form pockets that fill
  with water and break off as vacuoles in the
  cytoplasm

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Exocytosis

• Membrane of vacuole fuses with cell membrane
• Forces contents out of cell

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Osmosis

• Diffusion of water through a selectively
  permeable membrane
• Water moves from an area of high water
  concentration to an area of low water
  concentration

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Figure 7-15

• In the beaker on the left, which solution is
  hypertonic and which is hypotonic?
• The solution on the left side of the membrane is
  hypertonic and the solution on the right is
  hypotonic
• In this model, to which material is the membrane
  permeable, water or sugar?
• Water!! This makes the membrane selectively
  permeable