Modeling Passive Diffusion of Oxygen
Practice
Directions:
1. Set up your model by showing
oxygen molecules as shown on
the left on either side of your
cell membrane.
2. Show how molecules move by
passive diffusion using your
model pieces.
3. Move the oxygen molecules
until they reach equilibrium.
Assessment
Questions for your model: Answer the
questions below and be prepared to
answer these questions for your
teacher.
1. Explain what causes oxygen
molecules to move across the
cell membrane.
2. What is passive diffusion?
3. What are some molecules that
can move by passive diffusion?
Modeling Passive Diffusion (Osmosis) of Water
Practice
Directions:
1. Create a semi-permeable cell
membrane from yarn. It will
allow water to pass, but not
sodium.
2. Set up your model with sodium
and water molecules as shown
on the left on either side of the
cell membrane.
3. Demonstrate osmosis by moving
the water molecules in your
model.
4. Practice moving water molecules
across the cell membrane until
they reach equilibrium.
Assessment
Questions for your model: Answer the
questions below and be prepared to
answer these questions for your
teacher.
1. Explain why water molecules
move across the membrane.
2. After the diffusion of water, how
much water is inside the cell
compared to outside the cell?
Why?
Modeling Facilitated Diffusion of Glucose
Practice
Directions:
1. Set up your model as shown
on the left. Place a protein
channel in the cell
membrane and glucose
molecules outside the cell
membrane.
2. Demonstrate facilitated
diffusion by moving glucose
molecules through the
protein channel.
3. Practice moving glucose
molecules across the cell
membrane until equilibrium
is reached.
Assessment
Questions for your model: Answer the
questions below and be prepared to
answer these questions for your
teacher.
1. Why do glucose molecules
require a protein channel?
2. How is the transport of glucose
similar to passive diffusion?
How is it different?
3. Why is the diffusion of glucose
“facilitated”
Modeling Active Transport of Sodium
Practice
Directions:
1. Set up your model as shown on
the left, with sodium, water,
and ATP on either side of the
cell membrane.
2. Demonstrate active transport
by moving the sodium
molecules across the protein
channel in your model. Recall,
in active transport molecules
require energy in the form of
ATP to cross the protein
channel.
3. Place an ATP molecule on the
protein channel to model
energy in this process.
4. You can move three sodium
molecules through the protein
channel with one ATP. Note:
The energy provided by ATP,
not concentration gradients,
moves molecules in active
transport. Molecules do not
need to reach equilibrium.
Assessment
Questions for your model: Answer the
questions below and be prepared to
answer these questions for your
teacher.
1. Describe and explain how
sodium molecules move across
the cell membrane.
2. What is necessary for a
molecule to move with active
transport?
3. Why do molecules like sodium
enter the cell by active
transport and not by passive
diffusion.
Cell A: Students should set up the cell as shown above (low in oxygen and
glucose). Students should use the concepts from practice to describe and model
how molecules move by active transport, osmosis, facilitated diffusion and/or
passive diffusion.
Cell B: Students should set up the cell as shown above (low in oxygen, water, and
sodium). Students should use the concepts from practice to describe and model
how molecules move by active transport, osmosis, facilitated diffusion and/or
passive diffusion.
Cell C: Students should set up the cell as shown above (low in oxygen, water,
glucose, and sodium). Students should use the concepts from practice to
describe and model how molecules move by active transport, osmosis, facilitated
diffusion and/or passive diffusion.