Station 3

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Station 3
Cell Structure and Function

• Transport of Molecules and Homeostasis

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Essential Question

• Why should a freshwater fish never be placed in a
  saltwater aquarium?
• Most freshwater fish do not have the mechanisms
  necessary to adjust to the high levels of salt,
  so the salt would cause their cells to shrivel
  and die.

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Pre-Preview Questions

• The diffusion of water molecules in and out of
  cells is called?
• Cyclosis
• Osmosis
• Active transport
• Homeostasis

4
Pre-Preview Questions

• A red blood cell placed in distilled water will
  swell and burst due to the diffusion
• of ?
• Salts from the cell to the water.
• Water into the red blood cell.
• Water from the blood cell into its environment.
• Salts from the water into the red blood cell.

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Pre-Preview Questions

• What would happen if you watered a plant with
  salt water?
• The cells would shrivel and pull away from the
  cell wall.
• The blood cells would lyse (burst) and break the
  cell wall.
• The plant would be rehydrated.
• The plant would grow faster.

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1. Copy the table into your journal and fill in the
   data.

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2. Using the information recorded in the data
tables, draw the beakers, potatoes, and arrows
showing which way the water would be going.
Solution A Solution B Solution
C 25 g. sugar 150 g. sugar
distilled water
3. Determine which beaker contains a hypertonic
solution, which contains a hypotonic solution,
and which contains an isotonic solution.
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2. Using the information recorded in the data
tables, draw arrows on the beakers below to
illustrate what happened to the potato cores in
each of the different solutions.
Solution A Solution B
Solution C 25 g. sugar 150 g. sugar
distilled water
Hypotonic
Hypertonic
Isotonic
3. Determine which beaker contains a hypertonic
solution, which contains a hypotonic solution,
and which contains an isotonic solution.
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I need to remember

• Osmosis is the movement of water molecules across
  a semi-permeable membrane.
• Sometimes the movement of molecules across a
  semipermeable membrane requires energy.
• When the number of molecules inside a cell is
  equal to the number of molecules on the outside
  of the cell, homeostasis has been reachedthe
  cell is in equilibrium.

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True or False
If fertilizer, containing a lot of salt ions, is
placed on grass, water will move into the grass
cells causing them to become turgid. False
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True or False
Water molecules can diffuse across the cell
memebrane. True
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True or False
If a potato is soaking in a hypotonic solution,
it will lose mass. False
13
True or False
Salt ions can passively diffuse across the cell
membrane. False