3.4 Diffusion and Osmosis
Somewhere on pg. 28
If the cell membrane was rigid
(solid or hard), as opposed to
fluid (oil or liquid like), explain
why the membrane would no
longer be selectively
permeable.
3.4 Diffusion and Osmosis
If the membrane was rigid:
• The phospholipids would not be able to move
from side to side or slide past one another
• The phospholipids would be
unable to move to allow material
in or out!
3.3 Cell Membrane
Sponge: Set up Cornell
Notes on pg. 31
Topic: 3.4 Diffusion
Essential Question:
Explain what a
concentration gradient is
and what it means for a
molecule to diffuse down
its concentration gradient.
3.4 Diffusion
2.1 Atoms, Ions,
and Molecules
Explain what a concentration gradient
is and what it means for a molecule to
diffuse down its concentration
gradient.
Key Concept: Materials move
across membranes because of
concentration differences.
3.4
and Osmosis
3.3 Diffusion
Cell Membrane
Standard
1.a Students know cells are enclosed within a
semipermeable membranes that regulate their
interaction with their surroundings.
3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes
because of concentration differences.
3.4 Diffusion and Osmosis
Solution: A homogenous mixture of two or more substances,
which may be solids, liquids, or gases, or the combination of
these.
Ex: Sugar water
Solute: Substance dissolved in another substance
Ex: Sugar
Solvent: Substance doing the dissolving (usually the substance
present in the greatest amount)
Ex: Water (THE BEST SOLVENT)
Which one is the Solute? Solvent? Solution?
Milk
Solvent
Air
Solution
Chocolate Milk
Solution
Chocolate Syrup
Solute
Nitrogen (78%)
Oxygen, argon, CO2 (22%)
Solvent
Solute
3.4 Diffusion and Osmosis
• Passive transport- the movement of molecules across a
cell membrane without energy input from the cell
• There are two types of
passive transport.
1. diffusion
2. osmosis
Diffusion Demonstration
Materials: 2 Cups, Water, Dye, Salt, Graph
1)
2)
3)
4)
Identify the solvent, solute, and solution for
each demonstration
Hypothesize what is going to happen when
you drop the food coloring in the water. Salt
in the water?
Did your hypothesis match the results?
Explain how these experiments
demonstrated diffusion
Colored H2O
Salt Water
Solvent
Solute
Solution
Hypothesis: What is going to Dye is added
happen when….
Salt is added
What happened after 5 mins?
Was your hypothesis right?
How did these experiments
demonstrate diffusion?
Pg. 30
3.4 Diffusion and Osmosis
Diffusion: is the movement of molecules in a fluid or
gas from a region of higher concentration to a
region of lower concentration.
3.4 Diffusion and Osmosis
Diffusion: is the movement of molecules in a fluid or
gas from a region of higher concentration to
a region of lower concentration.
3.4 Diffusion and Osmosis
Diffusion: is the movement of molecules in a fluid or
gas from a region of higher concentration to a region
of lower
concentration.
Air Freshener Demo.
• Concentration gradient- the difference in the concentration
of a substance from one location to another.
•Molecules diffuse down their concentration gradient
Top ¼ pg. 30
3.3 Cell Membrane
Sponge: Set up Cornell
Notes on pg. 33
Topic: 3.4 Osmosis
Essential Question:
A cell is bathed in fluid.
However, you notice that
water is flowing out of the
cell. In what kind of
solution is this cell
immersed?
3.4 Osmosis
2.1 Atoms, Ions,
and Molecules
A cell is bathed in fluid. However, you
notice that water is flowing out of the
cell. In what kind of solution is this cell
immersed?
3.3 Cell Membrane
Isotonic Solution
Pg. 32
Hypertonic Solution
Hypotonic Solution
3.4 Diffusion and Osmosis
• Osmosis is the diffusion of water molecules across a
semipermeable membrane.
The water will continue to move across the
membrane until it reaches “equilibrium” or
an isotonic state
3.4 Diffusion and Osmosis
• There are three types of solutions.
• Same amount of
solutes/water inside
and outside cell
• = amounts of water
enter and leave the
cell
• Stays the same size!
3.4 Diffusion and Osmosis
• There are three types of solutions.
• More solutes outside
the cell than inside the
cell
• More water inside
the cell than outside
the cell
• More water exits cell
• Shrinks!
3.4 Diffusion and Osmosis
• There are three types of solutions.
• More solutes inside
the cell than outside the
cell
• More water outside
cell than inside the cell
• More water enters cell
• Expands!
Osmosis Videos
•
•
•
•
Osmosis vs. Diffusion
Osmosis Computer Graphics
Osmosis Demo Video
Osmosis with a U-tube
Gummi Bear Osmosis Lab
Table 1: Predictions and Conclusions
Starting
Information
Weight (g)
Predictions
Length (mm)
Conclusion
Sugar Water
Distilled Water
Salt Water
.
Width (mm)
Osmosis Lab Materials
Materials:
1 cup
1 Gummi Bear
Ruler (mm)
Salt
1)
Water
Sugar
Scale (g)
String (for width)
Label each cup: First/Last Name Period #
Day One: Gathering Data
1)
Weigh your Gummi Bear and record its
weight (g)
2)
Measure your Gummi’s length and width
(mm)
3)
Place the Gummi in a 25/75 sugar/water
solution
4)
Fill in your table with your hypothesis
Day Two: Gathering Data
Dry your Gummi bear off carefully
2) Weigh your Gummi Bear and record its weight (g)
3) Measure your Gummi’s length and width (mm)
4) Was your hypothesis correct? What happened to
your Gummi? Compare this data with your group
data, and record on Lab report tables.
1)
Rinse out your cup and rinse off your gummi
(quick and carefully)
6) Place the Gummi in a 100% distilled water
5)
7)
Fill in your table with your new hypothesis
Day Three: Gathering Data
Dry your Gummi bear off carefully
2) Weigh your Gummi Bear and record its weight (g)
3) Measure your Gummi’s length and width (mm)
4) Was your hypothesis correct? What happened to
your Gummi? Compare this data with your group
data, and record on Lab report tables.
1)
Rinse out your cup and rinse off your gummi
(quick and carefully)
6) Place the Gummi in a 25/75 solution of salt and
water
7) Fill in your table with your new hypothesis
5)
3.4 Diffusion and Osmosis
• Some molecules cannot easily diffuse across the cell
membrane Ex: H2O
• Facilitated diffusion is
diffusion through transport
proteins
• Things like H2O would be
repelled by the
phospholipid tails, so
transport proteins allow the
H2O to diffuse easily
Pg. 32 Diffusion and Osmosis Video Notes
•
•
•
Osmosis in the kitchen
Osmosis with an Egg
Desalination- Reverse Osmosis