1. Do Now: Answer the following Questions.
What is the function of the cell membrane?
Do animals, plants, or both have a cell membrane?
What does a plant have surrounding the cell in addition to a cell membrane?

2. Announcements
Organelle Quiz - Friday!

3. Cell Membrane Function
Objective: To be able to understand the function of the cell membrane as it relates to diffusion, osmosis, and active transport.

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Cell Membrane
Cell Membrane
Outside of cell
Cell membrane
Inside of cell (cytoplasm)
Protein channel
Proteins
Lipid bilayer
Carbohydrate chains
The cell membrane regulates what enters and leaves the cell.
Students should write down the definition of homeostasis:  maintaining an internal stable environment (example: hot-sweat/cold-shiver/high blood glucose-insulin)
Functions
Regulates what goes in and out of a cell
Maintains homeostasis
Characteristics
Lipid bilayer that carries a charge
Protein channels
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5. Copyright Pearson Prentice Hall
Cell Membrane
Cell Membrane
Outside of cell
Cell membrane
Inside of cell (cytoplasm)
Protein channel
Proteins
Lipid bilayer
Carbohydrate chains
The cell membrane regulates what enters and leaves the cell.
2 ways to enter or leave a cell
Passive Transport (Diffusion)
Through the membrane
Through a protein channel
Active Transport
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6. Have pores (holes) in it Selectively permeable (semi-permeable)
Cell membranes
Have pores (holes) in it
Selectively permeable (semi-permeable)
Allowing some molecules in and keeps other molecules out.
Materials are moved through membrane by passive transport or active transport
Explain the “too large or too charged” idea
Use the example of a spaghetti colander as a semi-permeable - water through/spaghetti-not

7. Types of Cellular Transport
high
low
Weeee!!!
Passive Transport
(High Concentration to Low Concentration)
cell doesn’t use energy
Diffusion
Facilitated Diffusion
Osmosis
Active Transport
(Low Concentration to High Concentration)
cell does use energy
high
low
This is going to be hard work!!
Define concentration- the amount of a certain molecule (item) in a given space.

8. Before we can discuss cellular transport, let’s review some terms
Solution
A solution is a mixture of two or more substances.
Examples: Lemonade
Solute – substance that is dissolved (powder)
Solvent – material that is dissolving the substance (water)
Concentration = the mass of solute (mass of powder) in a given volume of solution (volume of water), or mass/volume.
Perhaps have a demo?  Salt in Water.  You could mix Kool-Aid- they could see the color difference to represent the solute is less in one versus the other.
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9. Passive Transport: Diffusion
What Happens During Diffusion?
Particles move from high concentration to low concentration
When the concentration of the particles is the same throughout a system, the system has reached equilibrium.
Spray an odor into the air at this point. Point out that the people near where the spray was emitted can smell it very strongly. The remainder of the room may begin to smell a fainter odor as the particles spread out. When the entire room smells the same, it is at equilibrium.
Point out this can happen in a solution as well.
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10. Copyright Pearson Prentice Hall
Simple Diffusion Through Cell Boundaries – molecules can pass directly through the cell membrane. High to low.
Time
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
A: High concentration of solute on the outside
B: Solute begins moving through cell membrane due to random movements
C: Equal concentrations of solute on either side of the membrane
A B C
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11. Diffusion continued…
Some molecules are too large or charged, to pass through the membrane using simple diffusion.
How will the cell reach equilibrium with the external environment?
Ask students for their ideas on how equilibrium is reached?

12. Facilitated Diffusion (High Concentration to Low Concentration)
Diffusion of specific particles using protein channels found in the membrane
Protein channels allow only specific molecules through (large or too charged)
Still considered a form of passive transport
Facilitated diffusion (Protein channel)
To break up the class, I may ask volunteer students to stand up and demonstrate how they can replicate a protein channel by allowing some students through and some not

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Osmosis
What is osmosis?
Osmosis the diffusion of water through a selectively permeable membrane (semi-permeable)
Students should note that the two parts of the definition they need to know are: diffusion of water, and semipermeable membrane.
Time
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14. Which way will the water move?
Students should draw a replica of the same u-tube and draw arrows to show which way the water will move and the level of the water on each side of the tube
Selectively permeable membrane

15. Which way will the water move?

16. Watch this Video! Pay attention to when the following terms are mentioned
Egg Osmosis
Isotonic -
Hypertonic -
Hypotonic -

17. Write a definition for the following terms related to osmosis based on the pictures (Describe which way the water is moving).
Isotonic -
Hypertonic -
Hypotonic -

18. Exit Slip: What are two differences between diffusion and osmosis
Exit Slip: What are two differences between diffusion and osmosis? Give an example of each. 1. 2.
What does diffusion, facilitated diffusion, and osmosis all have in common?
Diffiusion is the movement of particles from high concentration to low concentration (perfume spray in a room)
Osmosis is the movement of water from high concentration (of water) to low concentration (of water) through a semipermeable membrane (salt and fresh water separated
by a semipermeable membrane).
Movement of particles from high concentration to low concentration