Download Coordinated Science II Osmosis and Diffusion Practice Problems

Coordinated Science II
Osmosis and Diffusion Practice Problems
Name:_________________________________________ Date:______________ Class:______
1. Define the following terns
a. Osmosis- when water moves across a semi-permeable memebrane from a high
water potential to a low water potential
b. Diffusion- the movement of molecules down a concentration gradient form high
concentration to low concentration
c. Concentration gradient- the difference in the concentration of a substance from
one location to another
d. Hypertonic- water leaves the cell to enter the more concentrated solution
e. Isotonic- Water enters and leaves at the same rate
f. Hypotonic- water enters the cells since the cytoplasm is more concentrated
2. For each example below, explain if it describes (i) diffusion, (ii) osmosis, or (iii) neither.
Explain your answer in each case.
a. Water moves from a dilute solution in the soil into the cells in a plant’s roots.
ii- water is moving from a high water potential to a low water potential
b. Saliva flows out of the salivary glands into your mouth.
iii- neither
c. A spot of blue ink dropped into a glass of still water quickly colors all the water
blue.
i- diffusion since the ink molecules are moving from a high concentration
to a low concentration.
Coordinated Science II
Osmosis and Diffusion Practice Problems
d. Carbon dioxide goes into a plant’s leaves when it is photosynthesizing.
ii-diffusion, carbon dioxide is moving from a high concentration to a low
concention
3. Explain each of the following.
a. Diffusion happens faster when the temperature rises.
The molecules of solution that are heating up are moving faster and therefore
spreading the solution faster
b. Oxygen diffuses out of a plant leaf during daylight hours.
Oxygen is moving from the high concentration inside the leaf to low
concentration in the air
c. Water molecules can pass through dialysis tubing, but starch molecules cannot.
Water molecules can pass through tubing due to its small size, starch molecules
are too large to pass through the semi-permeable tubing.
d. An animal cell bursts if placed in pure water.
The animal cell takes in the water, but since the animal cell does not have a cell
wall to push back on the growing pressure of the cell membrane, the cell
membrane will burst.
e. If a plant is short of water, its leaves lose their firmness and the plant wilts.
Is there is not enough water in the cell, then the cell membrane won’t be pushing
against the cell wall and therefore the cells are not firm.
4. The drawing shows the outline of a human cell. Copy the drawing and make two further
drawings to show how the cell would appear if it were to be
immersed for a few minutes in a solution with:
a. a lower water potential than its own cytoplasm
Coordinated Science II
Osmosis and Diffusion Practice Problems
Drawing should show shriveled cell given that the water has been removed from
the cell into the solution
b. a higher water potential than its own cytoplasm.
Drawing should show an inflated cell, or a cell exploding since the water is going
from the outside to the inside.
5. The graph shows the concentration of a
substance inside and outside a cell. If the
substance is free to move by diffusion,
which way will it move?
From the cytoplasm to the outside cell
a. If, after some hours, the
concentration has not changed, what
assumption would you make about
the movement of the substance across the cell membrane?
There are too large to cross through the memebrane
6. Cereal plants were growing in a field. The field was then flooded with sea water. Suggest
why the sea water causes plants to die.
The sea water would create a hypertonic environment where water is rushing from the
cells into the salt water solution. The water loss results in cells being plasmolyzed and not
being able to function correctly
7. Each of these statements was made by a candidate in an examination. Each one contains at
least one error. Decide what is wrong with each statement and rewrite it correctly.
a. If dialysis tubing containing a sugar solution is put into a beaker of water, the sugar
solution moves out of the tubing by osmosis.
If a dialysis tubing containing a sugar solution is put into a beaker of water, the water
moves into the tubing by osmosis.
Coordinated Science II
Osmosis and Diffusion Practice Problems
b. Plant cells do not burst in pure water because the cell wall stops water getting into the
cell.
Plants cells do not burst in pure water because the cell wall pushes back against the cell
membrane.
c. Animal cells break away from the cell wall in a concentrated sugar solution.
Animal cells membrane shrivel up in a concentrated sugar solution.
d. When a plant cell is placed in a concentrated sugar solution, water moves out of the cell
by osmosis through the partially permeable cell wall.
When a plant cell is placed in a concentrates sugar solution, water moves out of the cell
by osmosis through the partially permeable cell membrane.
8. The diagram at the right represents (not to scale) molecules of a salt
dissolved in the bottom layer of water in a beaker. Make two similar
diagrams to show the distribution of salt molecules (a) after a few minutes,
(b) after several hours.
a. the salt molecules will be diffusing upwards
b. the salt molecules are throughout the beaker
9. When meat is salted, bacteria cannot grow on it. Suggest a reason for this.
The meat has low water potential, and bacteria would have high water potential therefore
the water will move from the high water potential of the bacteria to the low water
potential of the meat.
10. The diagram at the right shows a vessel that contains a
concentrated and a dilute solution separated by a partially
permeable membrane. Draw a similar diagram to show the liquid
levels after an hour or two.
The dilute solution should be lower because it is going from a
dilute solution to a concentrated one
Coordinated Science II
Osmosis and Diffusion Practice Problems