Cell Structure and
Function
Station 3
Transport of Molecules and Homeostasis
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.
Pre-Preview Questions
• The diffusion of water molecules in and
out of cells is called?
A. Cyclosis
B. Osmosis
C. Active transport
D. Homeostasis
Pre-Preview Questions
• A red blood cell placed in distilled water
will swell and burst due to the diffusion
of ?
A. Salts from the cell to the water.
B. Water into the red blood cell.
C. Water from the blood cell into it’s
environment.
D. Salts from the water into the red blood
cell.
Pre-Preview Questions
• What would happen if you watered a plant
with salt water?
A. The cells would shrivel and pull away
from the cell wall.
B. The blood cells would lyse (burst) and
break the cell wall.
C. The plant would be rehydrated.
D. The plant would grow faster.
1.Copy
the
table
into
your
journal
and fill
in the
data.
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
25 g. sugar
Solution B
150 g. sugar
Solution C
distilled water
3. Determine which beaker contains a hypertonic solution,
which contains a hypotonic solution, and which contains an
isotonic solution.
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
25 g. sugar
Hypotonic
Solution B
150 g. sugar
Hypertonic
Solution C
distilled water
Isotonic
3. Determine which beaker contains a hypertonic solution,
which contains a hypotonic solution, and which contains an
isotonic solution.
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 reached—the
cell is in equilibrium.
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
True or False
Water molecules can diffuse across the
cell memebrane.
True
True or False
If a potato is soaking in a hypotonic
solution, it will lose mass.
False
True or False
Salt ions can passively diffuse across
the cell membrane.
False