DIFFUSION ACTIVITY
Recall Prior Knowledge:
1. Cell membrane regulates what enters and leaves the cell
2. Small nonpolar molecules easily pass through the plasma membrane
3. Oxygen and carbon dioxide are small nonpolar molecules
4. Solute is a substance that dissolves to form a solution
5. Solvent is the substance in which a solutes dissolves
6. A mixture of one or more solutes dissolved in a solvent
HOW DO SUBSTANCES ENTER AND LEAVE THE CELL?
Activity 1:
Demonstration
Materials:
3 beakers
Water warm and cold
Food dye
Raisins
1. Add regular tap water to a small beaker and then add raisins (put aside for
now)
2. Add warm water to a second beaker and cold water to a third beaker
3. Add a drop of food dye to the cold and warm water
Class Discussion of observations:
1.
2.
3.
4.
5.
6.
What do you see happening?
Is it occurring faster in one beaker than the other? Why might that be?
Is there an overall direction of movement?
Is an outside energy source required?
What is name of this process?
Can anybody define diffusion?
IF RAISINS ARE READY CAN DISCUSS NOW (if not wait to after next activity)
1.
2.
3.
4.
Do you observe any changes? What changed
Why did the raisin swell up?
Why did the water change colors?
Where do you think the greater concentration of iodine was? Inside or
outside raisins?
5. Do you think iodine is a small or large molecule, polar or nonpolar? Why?
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Activity 2:
Analyzing a diagram
LOOK AT THE DIAGRAM ABOVE AND ANSWER THE QUESTIONS BELOW:
a. Diffusion of one solute-top diagram
1. Initially (in the first picture on left),is there a difference between the
concentrations of purple dye on the left side of the membrane compared to
right side of membrane?
2. Are the purple dye molecules moving?
3. What is responsible for any movement of the purple dye molecules?
4. Are the purple molecules moving in both directions across the membrane?
5. Overall, are more purple dye molecules moving to the left or to the right?
6. Ultimately, what does this result in?
b. Diffusion of two solutes-bottom diagram
1. Initially where is the concentration of purple dye the greatest?
2. Initially, where is the concentration of blue dye the greatest?
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3. Do both purple dye and blue dye molecules have random motion (kinetic
energy)?
4. Overall, are more purple dye molecules moving to the left or to the right?
5. Overall, are more blue dye molecules moving to the left or to the right?
6. When does diffusion end?
7. Did the concentration of one solute affect the diffusion of the other solute?
8. Can you now define the following:
a. Diffusion
b. Concentration gradient
c. Random motion of molecules
d. Going with or down the concentration gradient
e. Going against or up the concentration gradient?
f. Dynamic equilibrium
9. How do you think the steepness of concentration gradient effects diffusion?
10. Can diffusion occur without a concentration gradient?
11. Was any input of energy required?
Class discussion
Activity 3:
Animation
View the following animation and answer questions below:
Note: think of partial pressure as concentration
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter25/animation__gas_exchange_d
uring_respiration.html
1. In the lungs where is there a higher concentration of oxygen, in the air sacs
(alveoli) or the blood cells?
2. Which way will oxygen diffuse-into lung cells or red blood cells? Why?
3. What keeps the oxygen concentration higher in lung cells than red blood
cells?
4. In the lungs where is there a higher concentration of carbon dioxide, in the
air sacs (alveoli) or the blood cells?
5. Which way will carbon dioxide diffuse –into lung cells or red blood cells?
6. What keeps the carbon dioxide level lower in lung cells than the red blood
cells?
7. Blood carries oxygen to all the cells of the body. Where is the oxygen
concentration higher-Blood or the cells of body?
8. Which way will oxygen diffuse-into blood or into cells of body? Why?
9. What keeps oxygen concentration lower in the cells of the body?
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10. Is the carbon dioxide concentration greater in the cells of body or in the
blood?
11. Which way will carbon dioxide diffuse-into the blood or into the cells of
body? Why?
12. How do the cells of the body keep their concentration of carbon dioxide
higher than the blood?
NOTE THAT THE ONLY WAY OXYGEN ENTERS YOUR CELLS, WHICH IS NEEDED
FOR CELL RESPIRATION IS BY DIFFUSION. THE ONLY WAY CARBON DIOXIDE
(TOXIC) PRODUCED DURING CELL RESPIRATION CAN LEAVE CELLS IS BY
DIFFUSION.
Activity 4:
Fill in class notes
Activity 5:
Check for understanding:
Dispense quiz questions
Discussion
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